Elastic touch input surface

ABSTRACT

A device including an elastic layer that, when depressed by an object, causes a local indentation in the layer, the geometry of the local indentation being in accordance with a force of depression, light emitters, light detectors, a light guide between the emitters and the layer directing light beams from the emitters into the layer at an angle such that the light beams, after entering the layer, remain confined to the layer by total internal reflection, a light guide between the detectors and the layer that directs light beams exiting the layer onto the detectors, each detector having a reference output value corresponding to expected light detection when no object is touching the layer, and a processor determining the object&#39;s force of depression based on the geometry of the local indentation in the layer, as calibrated by a deviation between actual and reference output values for one of the detectors.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/731,023, now U.S. Pat. No. 9,158,416, entitled RESILIENT LIGHT-BASEDTOUCH SURFACE, and filed on Dec. 30, 2012 by inventors Thomas Erikssonand Michael Lawrence Elyan, the contents of which are herebyincorporated herein in their entirety. U.S. application Ser. No.13/731,023 claims priority benefit of U.S. Provisional PatentApplication Ser. No. 61/609,325, entitled RESILIENT LIGHT-BASED TOUCHSURFACE, and filed on Mar. 11, 2012 by inventors Thomas Eriksson andMichael Lawrence Elyan, the contents of which are hereby incorporatedherein in their entirety.

U.S. application Ser. No. 13/731,023 is a continuation-in-part of U.S.application Ser. No. 13/424,592, now U.S. Pat. No. 8,416,217, entitledLIGHT-BASED FINGER GESTURE USER INTERFACE, and filed on Mar. 20, 2012 byinventors Thomas Eriksson, Per Leine, Jochen Laveno Mangelsdorff, RobertPettersson and Anders Jansson, the contents of which are herebyincorporated herein in their entirety.

U.S. application Ser. No. 13/731,023 is a continuation-in-part of U.S.application Ser. No. 13/424,543, now U.S. Pat. No. 9,052,777, entitledOPTICAL ELEMENTS WITH ALTERNATING REFLECTIVE LENS FACETS, and filed onMar. 20, 2012 by inventors Stefan Holmgren, Lars Sparf, Magnus Goertz,Thomas Eriksson, Joseph Shain, Anders Jansson, Niklas Kvist, RobertPettersson and John Karlsson, the contents of which are herebyincorporated herein in their entirety.

U.S. application Ser. No. 13/424,592 claims priority benefit of U.S.Provisional Application Ser. No. 61/564,868, entitled LIGHT-BASED FINGERGESTURE USER INTERFACE, filed on Nov. 30, 2011 by inventors ThomasEriksson, Per Leine, Jochen Laveno Mangelsdorff, Robert Pettersson andAnders Jansson, the contents of which are hereby incorporated herein intheir entirety.

U.S. application Ser. No. 13/424,543 claims priority benefit of U.S.Provisional Application Ser. No. 61/564,164, entitled OPTICAL ELEMENTSWITH ALTERNATIVE REFLECTIVE LENS FACETS, filed on Nov. 28, 2011 byinventors Stefan Holmgren, Lars Sparf, Thomas Eriksson, Joseph Shain,Anders Jansson, Niklas Kvist, Robert Pettersson and John Karlsson, thecontents of which are hereby incorporated herein in their entirety.

U.S. application Ser. No. 13/424,543 claims priority benefit of PCTApplication No. PCT/US11/29191, entitled LENS ARRANGEMENT FORLIGHT-BASED TOUCH SCREEN, filed on Mar. 21, 2011 by inventors MagnusGoertz, Thomas Eriksson, Joseph Shain, Anders Jansson, Niklas Kvist,Robert Pettersson, Lars Sparf and John Karlsson, the contents of whichare hereby incorporated herein in their entirety.

U.S. application Ser. No. 13/424,543 is a continuation-in-part of U.S.application Ser. No. 12/371,609, now U.S. Pat. No. 8,339,379, entitledLIGHT-BASED TOUCH SCREEN, filed on Feb. 15, 2009 by inventors MagnusGoertz, Thomas Eriksson and Joseph Shain, the contents of which arehereby incorporated herein in their entirety.

U.S. application Ser. No. 13/424,543 is a continuation-in-part of U.S.Application Ser. No. 12/760,567, now U.S. Pat. No. 9,213,443, entitledOPTICAL TOUCH SCREEN SYSTEMS USING REFLECTED LIGHT, and filed on Apr.15, 2010 by inventors Magnus Goertz, Thomas Eriksson and Joseph Shain,the contents of which are hereby incorporated herein in their entirety.

U.S. application Ser. No. 13/424,543 is a continuation-in-part of U.S.application Ser. No. 12/760,568, entitled OPTICAL TOUCH SCREEN SYSTEMSUSING WIDE LIGHT BEAMS, filed on Apr. 15, 2010 by inventors MagnusGoertz, Thomas Eriksson and Joseph Shain, the contents of which arehereby incorporated herein in their entirety.

PCT Application No. PCT/US11/29191 claims priority benefit of U.S.Provisional Application Ser. No. 61/379,012, entitled OPTICAL TOUCHSCREEN SYSTEMS USING REFLECTED LIGHT, and filed on Sep. 1, 2010 byinventors Magnus Goertz, Thomas Eriksson, Joseph Shain, Anders Jansson,Niklas Kvist and Robert Pettersson, the contents of which are herebyincorporated herein in their entirety.

PCT Application No. PCT/US11/29191 claims priority benefit of U.S.Provisional Application Ser. No. 61/380,600, entitled OPTICAL TOUCHSCREEN SYSTEMS USING REFLECTED LIGHT, filed on Sep. 7, 2010 by inventorsMagnus Goertz, Thomas Eriksson, Joseph Shain, Anders Jansson, NiklasKvist and Robert Pettersson, the contents of which are herebyincorporated herein in their entirety.

PCT Application No. PCT/US11/29191 claims priority benefit of U.S.Provisional Application Ser. No. 61/410,930, entitled OPTICAL TOUCHSCREEN SYSTEMS USING REFLECTED LIGHT, filed on Nov. 7, 2010 by inventorsMagnus Goertz, Thomas Eriksson, Joseph Shain, Anders Jansson, NiklasKvist, Robert Pettersson and Lars Sparf, the contents of which arehereby incorporated herein in their entirety.

U.S. application Ser. No. 12/760,567 claims priority benefit of U.S.Provisional Application Ser. No. 61/169,779, entitled OPTICAL TOUCHSCREEN, filed on Apr. 16, 2009 by inventors Magnus Goertz, ThomasEriksson and Joseph Shain, the contents of which are hereby incorporatedherein in their entirety.

FIELD OF THE INVENTION

The field of the present invention is light-based touch screens.

BACKGROUND OF THE INVENTION

Many consumer electronic devices are now being built with touchsensitive screens, for use with finger or stylus touch user inputs.These devices range from small screen devices such as mobile phones andcar entertainment systems, to mid-size screen devices such as notebookcomputers, to large screen devices such as check-in stations atairports.

Most conventional touch screen systems are based on resistive orcapacitive layers. Such systems are not versatile enough to offer anall-encompassing solution, as they are not easily scalable.

Reference is made to FIG. 1, which is a prior art illustration of aconventional touch screen system. Such systems include an LCD displaysurface 606, a resistive or capacitive overlay 801 that is placed overthe LCD surface, and a controller integrated circuit (IC) 701 thatconnects to the overlay and converts inputs from the overlay tomeaningful signals. A host device (not shown), such as a computer,receives the signals from controller IC 701, and a device driver or suchother program interprets the signals to detect a touch-based input suchas a key press or scroll movement.

Reference is made to FIG. 2, which is a prior art illustration of aconventional resistive touch screen. Shown in FIG. 2 are conductive andresistive layers 802 separated by thin spaces. A PET film 803 overlays atop circuit layer 804, which overlays a conductive coating 806.Similarly, a conductive coating 807 with spacer dots 808 overlays abottom circuit layer 805, which overlays a glass layer 607. When apointer 900, such as a finger or a stylus, touches the screen, a contactis created between resistive layers, closing a switch. A controller 701determines the current between layers to derive the position of thetouch point.

Advantages of resistive touch screens are their low cost, low powerconsumption and stylus support.

A disadvantage of resistive touch screens is that as a result of theoverlay, the screens are not fully transparent. Another disadvantage isthat pressure is required for touch detection; i.e., a pointer thattouches the screen without sufficient pressure goes undetected. As aconsequence, resistive touch screens do not detect finger touches well.Another disadvantage is that resistive touch screens are generallyunreadable in direct sunlight. Another disadvantage is that resistivetouch screens are sensitive to scratches. Yet another disadvantage isthat resistive touch screens are unable to discern that two or morepointers are touching the screen simultaneously, referred to as“multi-touch”.

Reference is made to FIG. 3, which is a prior art illustration of aconventional surface capacitive touch screen. Shown in FIG. 3 is a touchsurface 809 overlaying a coated glass substrate 810. Two sides of aglass 811 are coated with a uniform conductive indium tin oxide (ITO)coating 812. In addition, a silicon dioxide hard coating 813 is coatedon the front side of one of the ITO coating layers 812. Electrodes 814are attached at the four corners of the glass, for generating anelectric current. A pointer 900, such as a finger or a stylus, touchesthe screen, and draws a small amount of current to the point of contact.A controller 701 then determines the location of the touch point basedon the proportions of current passing through the four electrodes.

Advantages of surface capacitive touch screens are finger touch supportand a durable surface.

A disadvantage of surface capacitive touch screens is that as a resultof the overlay, the screens are not fully transparent. Anotherdisadvantage is a limited temperature range for operation. Anotherdisadvantage is a limited capture speed of pointer movements, due to thecapacitive nature of the touch screens. Another disadvantage is thatsurface capacitive touch screens are susceptible to radio frequency (RF)interference and electromagnetic (EM) interference. Another disadvantageis that the accuracy of touch location determination depends on thecapacitance. Another disadvantage is that surface capacitive touchscreens cannot be used with gloves. Another disadvantage is that surfacecapacitive touch screens require a large screen border. As aconsequence, surface capacitive touch screens cannot be used with smallscreen devices. Yet another disadvantage is that surface capacitivetouch screens are unable to discern a multi-touch.

Reference is made to FIG. 4, which is a prior art illustration of aconventional projected capacitive touch screen. Shown in FIG. 4 areetched ITO layers 815 that form multiple horizontal (x-axis) andvertical (y-axis) electrodes. Etched layers 815 include outer hard coatlayers 816 and 817, an x-axis electrode pattern 818, a y-axis electrodepattern 819, and an ITO glass 820 in the middle. AC signals 702 drivethe electrodes on one axis, and the response through the screen loopsback via the electrodes on the other axis. Location of a pointer 900touching the screen is determined based on the signal level changes 703between the horizontal and vertical electrodes.

Advantages of projective capacitive touch screens are finger multi-touchdetection and a durable surface.

A disadvantage of projected capacitive touch screens is that as a resultof the overlay, the screens are not fully transparent. Anotherdisadvantage is their high cost. Another disadvantage is a limitedtemperature range for operation. Another disadvantage is a limitedcapture speed, due to the capacitive nature of the touch screens.Another disadvantage is a limited screen size, typically less than 5″.Another disadvantage is that surface capacitive touch screens aresusceptible to RF interference and EM interference. Yet anotherdisadvantage is that the accuracy of touch location determinationdepends on the capacitance.

Conventional optical touch screens project light beams from one edge ofthe screen, over and across the screen surface to where photo detectorsdetect the uninterrupted beams. Touches are detected when an objectplaced on the screen blocks one or more of the projected light beams,and some of the photo detectors do not detect the expected light.

A disadvantage of conventional optical touch screens is that theyrequire a raised bezel around the screen in order to project the lightbeams across the screen. This requirement is incompatible with someproduct designs that require a completely flat upper surface with theedges of the device being flush with the screen surface.

Another disadvantage of conventional optical touch screens is anartifact known as “ghosting”. Ghosting is manifested when a pointer suchas a finger completely blocks a light beam, and a second pointersituated inside the shadow of the blocked beam goes undetected, sincethe second pointer does not affect the amount of light that reaches thedetector.

It would thus be beneficial to provide touch screens that overcome thedisadvantages of conventional resistive and capacitive touch screensdescribed above, while enabling flush device designs and detectingmultiple objects in a single beam's path.

SUMMARY OF THE DESCRIPTION

Aspects of the present invention provide light-based touch screens withlight beams directed over and across a display though a solid or liquidlayer covering the display, for which locations of two or more pointerstouching the screen simultaneously may be unambiguously inferred.

There is thus provided in accordance with an embodiment of the presentinvention a touch screen for a computing device, including a housing, alayer of light-transmissive material mounted in the housing, includingan upper surface that is exposed to be touched by one or more objectsfrom outside of the housing, a plurality of light emitters mounted inthe housing underneath the upper surface, for emitting light beams, afirst lens assembly for directing the light beams emitted by the lightemitters into the layer at an angle such that the light beams, whenentering the layer, remain confined to the layer by total internalreflection at the upper and lower surfaces of the layer when the lightbeams are not absorbed by any of the objects touching the upper surface,a plurality of light detectors mounted in the housing underneath theupper surface, for detecting light beams and for generating outputsindicating the amounts of light detected, a second lens assembly fordirecting light beams at a surface of the layer towards one or more ofthe light detectors, and a calculating unit, mounted in the housing andconnected to the light receivers, for determining respective one or morelocations of the one or more objects touching the upper surface, basedon outputs of the light detectors, wherein light beams in the layer arepartially absorbed at the upper surface when they come into contact withany of the objects.

There is additionally provided in accordance with an embodiment of thepresent invention a touch screen for a computing device, including ahousing, a layer of light-transmissive material mounted in the housing,including an upper surface that is exposed for touch by one or moreobjects from outside of the housing, a plurality of light emittersmounted in the housing underneath the upper surface, for emitting lightbeams, a first lens assembly mounted in the housing for directing thelight beams emitted by the light emitters into the layer at an anglesuch that the light beams, when entering the layer, remain confined tothe layer by total internal reflection at the upper and lower surfacesof said layer, a plurality of light detectors mounted in the housingunderneath the upper surface, for detecting light beams and forgenerating outputs indicating the amounts of light detected, a secondlens assembly mounted in the housing for directing light beams at asurface of the layer towards one or more of the light detectors, and acalculating unit, mounted in the housing and connected to said lightreceivers, for determining respective one or more locations of the oneor more objects touching the upper surface, based on outputs of thelight detectors, wherein light beams in the layer are scattered backinto the layer at the upper surface when they come into contact with anyof the objects, so that the second lens assembly directs them to more ofthe light detectors than had they not been scattered.

There is further provided in accordance with an embodiment of thepresent invention a light-based touch sensitive device, including ahousing, a surface encased in the housing, a layer of elastic materialabove the surface, a plurality of light pulse emitters mounted in thehousing, that transmit light pulses through the layer, a plurality oflight pulse receivers mounted in the housing, that receive the lightpulses transmitted through the layer, and a calculating unit, mounted inthe housing and connected to the receivers, that determines a locationof a pointer that touches the layer and creates an impression in thelayer, based on outputs of the receivers.

There is yet further provided in accordance with an embodiment of thepresent invention a light-based touch sensitive device including ahousing, a surface encased in the housing, a layer of elastic materialabove the surface and forming an air gap between the surface and thelayer, a plurality of light pulse emitters mounted in the housing, thattransmit light pulses over and across the surface through the air gap, aplurality of light pulse receivers mounted in the housing, that receivethe light pulses, and a calculating unit, mounted in the housing andconnected to the receivers, that determines a location of a pointer thattouches the layer and creates an impression in the layer, based onoutputs of the receivers.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more fully understood and appreciated fromthe following detailed description, taken in conjunction with thedrawings in which:

FIG. 1 is a prior art illustration of a conventional touch screensystem;

FIG. 2 is a prior art illustration of a conventional resistive touchscreen;

FIG. 3 is a prior art illustration of a conventional surface capacitivetouch screen;

FIG. 4 is a prior art illustration of a conventional projectedcapacitive touch screen;

FIG. 5 is a simplified illustration of a touch screen detection channel,in accordance with an embodiment of the present invention;

FIG. 6 a simplified illustration of light beams orientated along ascreen axis in a touch screen system, in accordance with an embodimentof the present invention;

FIG. 7 is a simplified illustration of light beams spread across ascreen like a fan in a touch screen system, in accordance with anembodiment of the present invention;

FIG. 8 is a simplified illustration of combined transmitter-receiverelements distributed along a screen edge that create circular, orarc-shaped detection zones, in accordance with an embodiment of thepresent invention;

FIG. 9 is an illustration of a portion of a touch screen including aplurality of emitters that are positioned close together, wherein lightis guided by fiber optic light guides to locations along a first screenedge, in accordance with an embodiment of the present invention;

FIG. 10 is a diagram of a touch screen having 16 emitters and 16receivers, in accordance with an embodiment of the present invention;

FIGS. 11-13 are diagrams of the touch screen of FIG. 10, showingdetection of two pointers that touch the screen simultaneously, inaccordance with an embodiment of the present invention;

FIGS. 14 and 15 are diagrams of a touch screen that detects a two fingerglide movement, in accordance with an embodiment of the presentinvention;

FIG. 16 is a circuit diagram of the touch screen from FIG. 10, inaccordance with an embodiment of the present invention;

FIG. 17 is a simplified diagram of a light-based touch screen system, inaccordance with an embodiment of the present invention;

FIG. 18 is a simplified cross-sectional diagram of the touch screensystem of FIG. 17, in accordance with an embodiment of the presentinvention;

FIG. 19 is a simplified illustration of an arrangement of emitters,receivers and optical elements that enable a touch screen system todetermine a precise location of a fingertip touching the screen, inaccordance with an embodiment of the present invention;

FIG. 20 is a simplified illustration of an arrangement of emitters,receivers and optical elements that enable a touch screen system todetect a pointer that is smaller than the sensor elements, includinginter alia a stylus, in accordance with an embodiment of the presentinvention;

FIG. 21 is a simplified diagram of a touch screen with wide light beamscovering the screen, in accordance with an embodiment of the presentinvention;

FIG. 22 is a simplified illustration of a collimating lens, inaccordance with an embodiment of the present invention;

FIG. 23 is a simplified illustration of a collimating lens incooperation with a light receiver, in accordance with an embodiment ofthe present invention;

FIG. 24 is a simplified illustration of a collimating lens having asurface of micro-lenses facing an emitter, in accordance with anembodiment of the present invention;

FIG. 25 is a simplified illustration of a collimating lens having asurface of micro-lenses facing a receiver, in accordance with anembodiment of the present invention;

FIG. 26 is a simplified diagram of an electronic device with a wide-beamtouch screen, in accordance with an embodiment of the present invention;

FIG. 27 is a diagram of the electronic device of FIG. 26, depictingoverlapping light beams from one emitter detected by two receivers, inaccordance with an embodiment of the present invention;

FIG. 28 is a diagram of the electronic device of FIG. 26, depictingoverlapping light beams from two emitters detected by one receiver, inaccordance with an embodiment of the present invention;

FIG. 29 is a diagram of the electronic device of FIG. 26, showing thatpoints on the screen are detected by at least two emitter-receiverpairs, in accordance with an embodiment of the present invention;

FIG. 30 is a simplified diagram of a wide-beam touch screen, showing anintensity distribution of a light signal, in accordance with anembodiment of the present invention;

FIG. 31 is a simplified diagram of a wide-beam touch screen, showingintensity distributions of overlapping light signals from two emitters,in accordance with an embodiment of the present invention;

FIG. 32 is a simplified diagram of a wide-beam touch screen, showingintensity distributions of two sets of overlapping light signals fromone emitter, in accordance with an embodiment of the present invention;

FIG. 33 is a simplified diagram of a wide beam touch screen with emitterand receiver lenses that do not have micro-lens patterns, in accordancewith an embodiment of the present invention;

FIGS. 34 and 35 are simplified diagrams of a wide-beam touch screen withemitter and receiver lenses that have micro-lens patterns, in accordancewith an embodiment of the present invention;

FIG. 36 is a simplified diagram of a wide-beam touch screen with emitterand receiver lenses that do not have micro-lens patterns, in accordancewith an embodiment of the present invention;

FIG. 37 is a simplified diagram of a wide beam touch screen, withemitter and receiver lenses that have micro-lens patterns, in accordancewith an embodiment of the present invention;

FIG. 38 is a simplified diagram of two emitters with lenses that havemicro-lens patterns integrated therein, in accordance with an embodimentof the present invention;

FIG. 39 is a simplified diagram of two receivers with lenses that havemicro-lens patterns integrated therein, in accordance with an embodimentof the present invention;

FIG. 40 is a simplified diagram of a side view of a single-unit lightguide, in the context of an electronic device with a display and anouter casing, in accordance with an embodiment of the present invention;

FIG. 41 is a simplified diagram of side views, from two differentangles, of a lens with applied feather patterns on a surface, inaccordance with an embodiment of the present invention;

FIG. 42 is a simplified diagram of a portion of a wide-beam touchscreen, in accordance with an embodiment of the present invention;

FIG. 43 is a top view of a simplified diagram of light beams enteringand exiting micro-lenses etched on a lens, in accordance with anembodiment of the present invention;

FIG. 44 is a simplified diagram of a side view of a dual-unit lightguide, in the context of a device having a display and an outer casing,in accordance with an embodiment of the present invention;

FIG. 45 is a picture of light guide units, within the context of adevice having a PCB and an outer casing, in accordance with anembodiment of the present invention;

FIG. 46 is a top view of the light guide units of FIG. 45, in accordancewith an embodiment of the present invention;

FIG. 47 is a simplified diagram of shift-aligned emitters and detectorsfor a light-based touch screen, for detecting finger touches, inaccordance with an embodiment of the present invention;

FIG. 48 is a simplified illustration of finger touch detection on thescreen of FIG. 47, in accordance with an embodiment of the presentinvention;

FIG. 49 is a simplified diagram of a side view cutaway of a light guidewithin an electronic device, in accordance with an embodiment of thepresent invention;

FIG. 50 is a simplified diagram of a side view cutaway of a portion ofan electronic device and an upper portion of a light guide with at leasttwo active surfaces for folding light beams, in accordance with anembodiment of the present invention;

FIG. 51 is a simplified drawing of a section of a transparent opticaltouch light guide, formed as an integral part of a protective glasscovering a display, in accordance with an embodiment of the presentinvention;

FIG. 52 is a simplified illustration of the electronic device and lightguide of FIG. 50, adapted to conceal the edge of the screen, inaccordance with an embodiment of the present invention;

FIG. 53 is a simplified diagram of a light guide that is a single unitextending from opposite an emitter to above a display, in accordancewith an embodiment of the present invention;

FIG. 54 is a simplified diagram of a dual-unit light guide, inaccordance with an embodiment of the present invention;

FIG. 55 is a simplified diagram of a touch screen device held by a user,in accordance with an embodiment of the present invention;

FIG. 56 is a simplified diagram of a touch screen with wide light beamscovering the screen, in accordance with an embodiment of the presentinvention;

FIGS. 57-59 are respective simplified side, top and bottom views of alight guide in the context of a device, in accordance with an embodimentof the present invention;

FIG. 60 is a simplified illustration of a touch screen surrounded byemitters and receivers, in accordance with an embodiment of the presentinvention;

FIG. 61 is a simplified illustration of an optical element with anundulating angular pattern of reflective facets, shown from threeangles, in accordance with an embodiment of the present invention;

FIG. 62 is a simplified illustration of an optical element reflecting,collimating and interleaving light from two neighboring emitters, inaccordance with an embodiment of the present invention;

FIG. 63 is a simplified diagram of a multi-faceted optical element, inaccordance with an embodiment of the present invention;

FIG. 64 is a simplified graph showing the effect of various reflectivefacet parameters on light distribution for nine facets, in accordancewith an embodiment of the present invention;

FIG. 65 is a simplified illustration of a touch screen with a wide lightbeam crossing the screen, in accordance with an embodiment of thepresent invention;

FIG. 66 is a simplified illustration of a touch screen with two widelight beams crossing the screen, in accordance with an embodiment of thepresent invention;

FIG. 67 is a simplified illustration of a touch screen with three widelight beams crossing the screen, in accordance with an embodiment of thepresent invention;

FIG. 68 is a simplified graph of light distribution of a wide beam in atouch screen, in accordance with an embodiment of the present invention;

FIG. 69 is a simplified illustration of detection signals from threewide beams as a fingertip moves across a screen, in accordance with anembodiment of the present invention;

FIGS. 70-72 are simplified graphs of light distribution in overlappingwide beams in a touch screen, in accordance with an embodiment of thepresent invention;

FIG. 73 is a simplified graph of detection signals from a wide beam as afingertip moves across a screen at three different locations, inaccordance with an embodiment of the present invention;

FIG. 74 is a simplified diagram of four optical elements and fourneighboring emitters, in accordance with an embodiment of the presentinvention;

FIG. 75 is a simplified diagram of a diffractive surface that directsbeams from two emitters along a common path, in accordance with anembodiment of the present invention;

FIG. 76 is a simplified diagram of a touch screen surrounded withalternating emitters and receivers, in accordance with an embodiment ofthe present invention;

FIG. 77 is a simplified illustration of a touch screen surrounded withalternating emitters and receivers, and a wide beam crossing the screen,in accordance with an embodiment of the present invention;

FIG. 78 is a simplified illustration of a touch screen surrounded withalternating emitters and receivers and two wide beams crossing thescreen, in accordance with an embodiment of the present invention;

FIG. 79 is a simplified illustration of a touch screen surrounded withalternating emitters and receivers and three wide beams crossing thescreen, in accordance with an embodiment of the present invention;

FIG. 80 is a simplified illustration of a collimating optical elementreflecting and interleaving light for an emitter and a neighboringreceiver, in accordance with an embodiment of the present invention;

FIGS. 81-84 are illustrations of multi-touch locations that areambiguous vis-à-vis a first orientation of light emitters, in accordancewith an embodiment of the present invention;

FIGS. 85-87 are illustrations of the multi-touch locations of FIGS.81-83 that are unambiguous vis-à-vis a second orientation of lightemitters, in accordance with an embodiment of the present invention;

FIG. 88 is a simplified illustration of a touch screen with light beamsdirected along four axes, in accordance with an embodiment of thepresent invention;

FIG. 89 is a simplified illustration of an alternate configuration oflight emitters and light receivers with two grid orientations, inaccordance with an embodiment of the present invention;

FIG. 90 is a simplified illustration of a configuration of alternatinglight emitters and light receivers, in accordance with an embodiment ofthe present invention;

FIG. 91 is a simplified illustration of two wide light beams from anemitter being detected by two receivers, in accordance with anembodiment of the present invention;

FIG. 92 is a simplified illustration of two wide beams and an area ofoverlap between them, in accordance with an embodiment of the presentinvention;

FIG. 93 is a simplified illustration of a touch point situated at theedges of detecting light beams, in accordance with an embodiment of thepresent invention;

FIG. 94 is a simplified illustration of a finger-sized touch point in ascreen designed for finger touch detection, in accordance with anembodiment of the present invention;

FIG. 95 is a simplified illustration of an emitter along one edge of adisplay screen that directs light to receivers along two edges of thedisplay screen, in accordance with an embodiment of the presentinvention;

FIGS. 96 and 97 are simplified illustrations of a lens for refractinglight in three directions, having a lens surface with a repetitivepattern of substantially planar two-sided and three-sided recessedcavities, respectively, in accordance with embodiments of the presentinvention;

FIGS. 98-100 are simplified illustrations of a touch screen surroundedwith alternating emitters and receivers and diagonal wide beams crossingthe screen, in accordance with an embodiment of the present invention;

FIG. 101 is a simplified graph of light distribution across a diagonalwide beam in a touch screen, in accordance with an embodiment of thepresent invention;

FIG. 102 is a simplified graph of light distribution across threeoverlapping diagonal wide beams in a touch screen, in accordance with anembodiment of the present invention;

FIG. 103 is a simplified graph of touch detection as a finger glidesacross three overlapping diagonal wide beams in a touch screen, inaccordance with an embodiment of the present invention;

FIG. 104 is a simplified graph of detection signals from a diagonal widebeam as a fingertip moves across the screen at three differentlocations, in accordance with an embodiment of the present invention;

FIG. 105 is a simplified illustration of a first embodiment for a touchscreen surrounded with alternating emitters and receivers, wherebydiagonal and orthogonal wide beams crossing the screen are detected byone receiver, in accordance with an embodiment of the present invention;

FIG. 106 is a simplified illustration of a second embodiment for a touchscreen surrounded with alternating emitters and reciters, wherebydiagonal and orthogonal wide beams crossing the screen are detected byone receiver, in accordance with an embodiment of the present invention;

FIG. 107 is a simplified illustration of a user writing on a prior arttouch screen with a stylus;

FIG. 108 is a simplified illustration of light beams detecting locationof a stylus when a user's palm rests on a touch screen, in accordancewith an embodiment of the present invention;

FIG. 109 is a simplified illustration of a frame surrounding a touchscreen, in accordance with an embodiment of the present invention;

FIG. 110 is a simplified illustration of a first embodiment of emitters,receivers and optical elements for a corner of a touch screen, inaccordance with an embodiment of the present invention;

FIG. 111 is a simplified illustration of a second embodiment ofemitters, receivers and optical elements for a corner of a touch screen,in accordance with an embodiment of the present invention;

FIG. 112 is an illustration of optical components made of plasticmaterial that is transparent to infrared light, in accordance with anembodiment of the present invention;

FIG. 113 is a simplified diagram of a side view of a touch screen withlight guides, in accordance with an embodiment of the present invention;

FIG. 114 is an illustration of a touch screen with a block of threeoptical components on each side, in accordance with an embodiment of thepresent invention;

FIG. 115 is a magnified illustration of one of the emitter blocks ofFIG. 114, in accordance with an embodiment of the present invention;

FIG. 116 is a simplified illustration of a touch screen assembly havinga cover glass, in accordance with an embodiment of the presentinvention;

FIG. 117 is a simplified illustration of a touch scattering internallyreflected light in a screen assembly having a cover glass, in accordancewith an embodiment of the present invention;

FIG. 118 is a simplified illustration of a touch object absorbinginternally reflected light in a screen assembly having a cover glass, inaccordance with an embodiment of the present invention;

FIG. 119 is a simplified illustration of a touch screen assembly havinga cover glass, in accordance with an embodiment of the presentinvention;

FIG. 120 is a simplified illustration of a light beam path in the touchscreen assembly of FIG. 119, in accordance with an embodiment of thepresent invention;

FIG. 121 is a simplified illustration of a touch screen assembly havinga cover glass, in accordance with an embodiment of the presentinvention;

FIG. 122 is a simplified illustration of emitters and receiversdetecting two diagonal touch points, in accordance with an embodiment ofthe present invention;

FIG. 123 is a simplified illustration of emitters and receiversdetecting three touch points, in accordance with an embodiment of thepresent invention;

FIG. 124 is a simplified illustration of a touch screen assembly havinga cover glass, in accordance with an embodiment of the presentinvention;

FIG. 125 is a flowchart of a method for disambiguating multiple touchdetection signals in accordance with an embodiment of the presentinvention;

FIG. 126 is a simplified illustration of a touch screen assembly havinga cover glass, in accordance with an embodiment of the presentinvention;

FIG. 127 is an illustration of a touch screen having a long thin lightguide along a first edge of the screen, for directing light over thescreen, and having an array of light receivers arranged along anopposite edge of the screen for detecting the directed light, and forcommunicating detected light values to a calculating unit, in accordancewith an embodiment of the present invention;

FIG. 128 is an illustration of a touch screen having an array of lightemitters along a first edge of the screen for directing light beams overthe screen, and having a long thin light guide for receiving thedirected light beams and for further directing them to light receiverssituated at both ends of the light guide, in accordance with anembodiment of the present invention;

FIG. 129 is an illustration of two light emitters, each emitter coupledto each end of a long thin light guide, in accordance with an embodimentof the present invention;

FIGS. 130-133 are illustrations of a touch screen that detectsoccurrence of a hard press, in accordance with an embodiment of thepresent invention;

FIGS. 134 and 135 are bar charts showing increase in light detected,when pressure is applied to a rigidly mounted 7-inch LCD screen, inaccordance with an embodiment of the present invention;

FIGS. 136 and 137 are illustrations of opposing rows of emitter andreceiver lenses in a touch screen system, in accordance with anembodiment of the present invention;

FIG. 138 is a simplified illustration of a technique for determining atouch location, by a plurality of emitter-receiver pairs in a touchscreen system, in accordance with an embodiment of the presentinvention;

FIG. 139 is an illustration of a light guide frame for the configurationof FIGS. 136 and 137, in accordance with an embodiment of the presentinvention;

FIG. 140 is a simplified flowchart of a method for touch detection for alight-based touch screen, in accordance with an embodiment of thepresent invention;

FIGS. 141-143 are illustrations of a rotation gesture, whereby a userplaces two fingers on the screen and rotates them around an axis;

FIGS. 144-147 are illustrations of touch events at various locations ona touch screen, in accordance with an embodiment of the presentinvention;

FIGS. 148-151 are respective bar charts of light saturation during thetouch events illustrated in FIGS. 144-147, in accordance with anembodiment of the present invention;

FIG. 152 is a simplified flowchart of a method for determining thelocations of simultaneous, diagonally opposed touches, in accordancewith an embodiment of the present invention;

FIG. 153 is a simplified flowchart of a method for discriminatingbetween clockwise and counter-clockwise gestures, in accordance with anembodiment of the present invention;

FIG. 154 is a simplified flowchart of a method of calibration and touchdetection for a light-based touch screen, in accordance with anembodiment of the present invention;

FIG. 155 is a picture showing the difference between signals generatedby a touch, and signals generated by a mechanical effect, in accordancewith an embodiment of the present invention;

FIG. 156 is a simplified diagram of a control circuit for setting pulsestrength when calibrating a light-based touch screen, in accordance withan embodiment of the present invention;

FIG. 157 is a plot of calibration pulses for pulse strengths rangingfrom a minimum current to a maximum current, for calibrating alight-based touch screen in accordance with an embodiment of the presentinvention;

FIG. 158 is a simplified pulse diagram and a corresponding output signalgraph, for calibrating a light-based touch screen, in accordance with anembodiment of the present invention;

FIG. 159 is an illustration showing how a capillary effect is used toincrease accuracy of positioning a component, such as an emitter or areceiver, on a printed circuit board, in accordance with an embodimentof the present invention;

FIG. 160 is an illustration showing the printed circuit board of FIG.159, after having passed through a heat oven, in accordance with anembodiment of the present invention;

FIG. 161 is a simplified illustration of a light-based touch screen andan ASIC controller therefor, in accordance with an embodiment of thepresent invention;

FIG. 162 is a circuit diagram of a chip package for a controller of alight-based touch screen, in accordance with an embodiment of thepresent invention;

FIG. 163 is a circuit diagram for six rows of photo emitters with 4 or 5photo emitters in each row, for connection to the chip package of FIG.162, in accordance with an embodiment of the present invention;

FIG. 164 is a simplified illustration of a touch screen surrounded byemitters and receivers, in accordance with an embodiment of the presentinvention;

FIG. 165 is a simplified application diagram illustrating a touch screenconfigured with two controllers, in accordance with an embodiment of thepresent invention;

FIG. 166 is a graph comparing scan sequence performance using aconventional chip vs. a dedicated controller of the present invention;

FIG. 167 is a simplified illustration of a touch screen having ashift-aligned arrangement of emitters and receivers, in accordance withan embodiment of the present invention;

FIG. 168 is a simplified diagram of a touch screen having alternatingemitters and receivers along each screen edge, in accordance with anembodiment of the present invention;

FIG. 169 is a simplified illustration of a touch surface with a flexiblecompressible layer on top of the surface, in accordance with anembodiment of the present invention;

FIG. 170 is a magnified view of the touch surface of FIG. 169, inaccordance with an embodiment of the present invention;

FIG. 171 is a simplified illustration of an object pressing down on theflexible compressible layer of the touch surface of FIG. 169, andcreating an impression thereon, in accordance with an embodiment of thepresent invention;

FIG. 172 is a simplified illustration of an alternative touch surfacewith a flexible compressible layer on top of the surface, in accordancewith an embodiment of the present invention;

FIG. 173 is a simplified illustration of an object pressing down on theflexible compressible layer of the touch surface of FIG. 172, andcreating an impression thereon, in accordance with an embodiment of thepresent invention; and

FIG. 174 is a simplified illustration of another alternative touchsurface with a flexible compressible layer on top of the surface, inaccordance with an embodiment of the present invention.

For reference to the figures, the following index of elements and theirnumerals is provided. Elements numbered in the 100's generally relate tolight beams, elements numbered in the 200's generally relate to lightsources, elements numbered in the 300's generally relate to lightreceivers, elements numbered in the 400's and 500's generally relate tolight guides, elements numbered in the 600's generally relate todisplays, elements numbered in the 700's generally relate to circuitelements, elements numbered in the 800's generally relate to electronicdevices, and elements numbered in the 900's generally relate to userinterfaces. Elements numbered in the 1000's are operations of flowcharts.

Similarly numbered elements represent elements of the same type, butthey need not be identical elements.

Element Description Elements generally related to light beams 100-102Light beams 105, 106 Reflected light beam 107-109 Arc of light outputfrom light source 110 Dist between centers of two beams 111 Dist fromemitter/rcvr to opt element 112 Refracted beam 113-117 Blocked lightbeams 120 Light beams (full intensity) 121 Light beams (partialintensity) 122 Scattered light beams 123 Absorbed light beams 142 Arc oflight output from light source 143 Arc of light input to light receiver144 Wide light beams 145-148 Edge of wide light beam 151-154 Light beams158 Wide light beam 167-169 Wide light beam 170-172 Signals received bylight receivers 173 Beam from 1 emitter to 2 receivers 174 Beam from 1emitter to 1^(st) receiver 175 Beam from 1 emitter to 2^(nd) receiver176 Beam from emitter to 1^(st) receiver 177 Beam from emitter to 2^(nd)receiver 178 Beam from 1 emitter to 1^(st) receiver 179 Beam from 1emitter to 2^(nd) receiver 182 Beam from 1 emitter to 2 receivers183-187 Middle of arc of light 190 Light beams output from light source191 Light beams input to light receiver 192 Arcs of light 193 Wide lightbeam from two sources 194-196 Arcs of light 197 Reflected light beamElements generally related to light sources 200-213 Light emitters 220LED cavity 230 Combined emitter-receiver elements 231-233 Combinedemitter-receiver elements 235-241 Light emitters Elements generallyrelated to light receivers 300-319 Light receivers 394 Light receiver398 Light receiver/light emitter Elements generally related to lightguides 400 Lens 401, 402 Fiber optic light guides 407 Raised reflectorbezel 408 Cutout 437, 438 Reflector & lens 439-443 Lens 444 Micro-lenses445 Surface with fan of micro-lenses 450 Light guide 451, 452 Internallyreflective surface 453, 454 Light guide surface 455 Light guide 456Internally reflective surface 457 Collimating lens & reflective surface458 Micro-lenses 459 Light guide surface 460 Surface with fan ofmicro-lenses 461 Lens 462 Micro-lenses 463 Upper portion of light guide464 Lower portion of light guide 465 Light guide surface 466 Surfacewith parallel row micro-lenses 467 Parallel row pattern of micro-lenses468 Light guide 469, 470 Internally reflective surface 471 Light guidesurface 472 Light guide 473 Internally reflective surface 474 Lightguide surface 475 Focal line of a lens 476 Light guide 477 Internallyreflective surface 478 Light guide surface 479 Light guide 480Internally reflective surface 481 Light guide surface 482 Black plastictransmissive element 483 Light guide 484 Surface with fan ofmicro-lenses 485 Upper portion of light guide 486 Lower portion of lightguide 487 Surface with parallel row micro-lenses 488, 489 Opticalcomponent 490-492 Surface of optical component 493 Multi-facetedreflective surface 494-497 Optical component 498, 499 Light guide500-501 Emitter optical component block 502-503 Receiver opticalcomponent block 504 Emitter lenses 505 Receiver lenses 506, 507 Emitteroptical component 508-510 Receiver optical component 511 Emitter opticalcomponents 512 Receiver optical components 513 Opticalcomponent/temporary guide 514 Long thin light guide 515 Light guidereflector 516 Micro-lenses 517 Light scatterer strip 518, 519 Lightguides 520, 521 Protruding lips on light guides 522, 523 Relativeposition of light guide element 524 Clear, flat glass 525 Collimatinglens 526 Clear flat glass with micro-lens surface 527 Lens with patternof refracting surfaces 528 Micro-lens pattern 530-534 Opt element withmulti-faceted surface 541 Optical element surface 542 Multi-facetedreflective surface 545-549 Reflective facets 550-552 Lens section inmulti-lens assembly 555, 556 Air gap 559 Connector joining lens section560 Diffractive surface 561 Optically clear transfer tape 562 Reflectivefacet 563 Air gap 564, 565 Light guide Elements generally related todisplays 600 Screen glass 606 LCD display (prior art) 607 Screen glass(prior art) 635-637 Display 638 Protective glass 639 Daylight filtersheet 640 Protective glass 641 Daylight filter sheet 642, 643 Display645 Cover glass 650 Resilient flexible layer Elements generally relatedto circuit elements 700 Printed circuit board 701 Controller integratedcircuit (pr. art) 702 AC input signal (prior art) 703 Output signal(prior art) 720 Shift register for column activation 730 Shift registerfor column activation 731 Chip package 732, 733 Signal conducting pins736 Input/output pins 737 Chip select pin 740 Emitter driver circuitry742 Emitter pulse control circuitry 750 Detector driver circuitry 753Detector signal processing circuitry 755 Detector current filter 756Analog-to-digital convertor 759 Controller circuitry 760, 761 Electricalpad 762, 763 Printed circuit board 764 Guide pin 765 Solder pad 766Component solder pad 767 Solder pads after heat oven 768, 769 Notch inoptical component/guide 770 Calculating unit 772 Host processor 774Touch screen controller 775 Serial Peripheral Interface (SPI) Elementsgenerally related to touch-based electronic devices 800 Touch screen 801Touch overlay (prior art) 802 Conductive & resistive layers (pr. art)803 PET film (prior art) 804 Top circuit layer (prior art) 805 Bottomcircuit layer (prior art) 806, 807 Conductive coating (prior art) 808Spacer dot (prior art) 809 Touch surface (prior art) 810 Coated glasssubstrate (prior art) 811 Glass substrate (prior art) 812 Conductive ITOcoating (prior art) 813 Silicon dioxide hard coating (prior art) 814Electrode (prior art) 815 Etched ITO layers (prior art) 816, 817 Hardcoat layer (prior art) 818 x-axis electrode pattern (prior art) 819y-axis electrode pattern (prior art) 820 ITO glass (prior art) 826Electronic device 827-832 Device casing 841, 842 Resilient members 843Flex air gap 844-847 Image sensors 849 Screen frame Elements generallyrelated to user interfaces 900-902 Pointer/finger/thumb/stylus 905Detected touch area 910-912 Light signal attenuation area 920, 921 Lightsignal attenuation gradient 925-927 Path across a wide beam 930 Hand 931Stylus 932 Drawn line 971, 972 Touch points 973-976 Light signalattenuation area 977 Point on lens 980 Touch point 981, 982 Point onlens 989, 990 Pin 991-993 Active touch area

DETAILED DESCRIPTION

Aspects of the present invention relate to light-based touch screens.

For clarity of exposition, throughout the present specification the term“touch screen” is used as a generic term to refer to touch sensitivesurfaces that may or may not include an electronic display. As such, theterm “touch screen” as used herein includes inter alia a mouse touchpadas included in many laptop computers, and the cover of a handheldelectronic device. The term “optical touch screen” is used as a genericterm to refer to light-based touch screens, including inter alia screensthat detect a touch based on the difference between an expected lightintensity and a detected light intensity, where the detected lightintensity may be greater than or less than the expected light intensity.

For clarity of exposition, throughout the present specification, theterm “emitter” is used as a generic term to refer to a light emittingelement, including inter alia a light-emitting diode (LED), and theoutput end of a fiber optic or tubular light guide that outputs lightinto a lens or reflector that directs the light over a display surface.The term “receiver” is used as a generic term to refer to a lightdetecting element, including inter alia a photo diode (PD), and theinput end of a fiber optic or tubular light guide that receives lightbeams that traversed a display surface and directs them to a lightdetecting element or to an image sensor, the image sensor being interalia a charge coupled device (CCD) or a complementary metal oxidesemiconductor (CMOS) image sensor.

A general principle underlying touch detection is that on object such asa finger, when placed on a screen, changes the coupling of light betweena transmitter and a receiver. The position of the finger is calculatedby determining how a signal changed and which transmitters and receiversare affected. By pulsing transmitters one at a time, it is determinedwhich transmitter sent light to a given receiver. The informationnecessary for touch detection is a signal indicating whether a finger istouching the screen, and a signal indicating where the touch is located.

Reference is made to FIG. 5, which is a simplified illustration of atouch screen detection channel, in accordance with an embodiment of thepresent invention. As shown in FIG. 5, between each transmitter and eachreceiver there is a channel for conducting signals. A channel signalindicates if there is a touch or not going through the channel. Asexplained below, when multiple touches occur at the same time, thesignal also encodes the number of touches in the channel. This case iscommonly referred to as “multi-touch”. There are two types of channels;namely,

-   -   A. channels for which a finger activates a signal between the        transmitter and the receiver; and    -   B. channels for which a finger blocks a signal between the        transmitter and the receiver.

For channel A, a low signal, near 0, indicates no touch, and a highsignal indicates a touch. Channel A extends to a channel A′, whichdetects more than one touch per channel. For channel A′, high signalvalues occur at different levels corresponding to the number of touches,where each touch added to the channel increases the signal by one step.

For channel B, a high signal indicates no touch, and a low signal, near0, indicates a touch. Channel B extends to a channel B′, which dividesthe signal value into multiple ranges or steps. Each additional touch inthe channel decreases the signal by one step.

FIGS. 6-8 illustrate different orientations of detection channelscovering a screen. Reference is made to FIG. 6, which is a simplifiedillustration of light beams orientated along a screen axis in a touchscreen system, in accordance with an embodiment of the presentinvention. FIG. 6 shows detection channels 100 along the width of screen635. Each channel begins at an emitter 200 at one edge of screen 635,and ends at a respective receiver 300 at the opposite edge of screen635.

Reference is made to FIG. 7, which is a simplified illustration of lightbeams spread across a screen like a fan in a touch screen system, inaccordance with an embodiment of the present invention. FIG. 7 showsdetection channels 100 spread out like a fan across a screen. All of thechannels begin at a single emitter 200 in one corner of the screen, andeach channel ends at a respective receiver 300 at an opposite edge ofthe screen.

Reference is made to FIG. 8, which is a simplified illustration ofcombined transmitter-receiver elements distributed along a screen edgethat create circular, or arc-shaped detection zones, in accordance withan embodiment of the present invention. FIG. 8(a) shows detectionchannels as circular zones 194-196 on screen 635. Each detection channelis created by an emitter-receiver element 231-233 that emits an arc oflight 194-196 and detects the reflection of an object inserted into thearc of light. The detection is shown in FIG. 8(b), where an object 900inserted into arc 194 reflects light beam 197 back onto emitter-receiverelement 231.

Reference is made to FIG. 9, which is an illustration of a portion of atouch screen including a plurality of emitters 201-203 that arepositioned close together, wherein light is guided by fiber optic lightguides 401 to locations along a first screen edge, in accordance with anembodiment of the present invention. The portion of the touch screenalso includes a plurality of receivers 301-305 that are positioned closetogether, wherein light is guided thereto by fiber optic light guides402 from locations along a second screen edge.

According to embodiments of the present invention, a light-based touchscreen includes one or more emitters, including inter alia infra-red ornear infra-red light-emitting diodes (LEDs), and a plurality ofreceivers, including inter alia photo diodes (PDs), arranged along theperimeter surrounding the touch screen or touch surface. The emittersproject light substantially parallel to the screen surface, and thislight is detected by the receivers.

In some embodiments, the projected light is transmitted through airabove the screen surface. A pointer, such as a finger or a stylus,placed over a portion of the screen blocks some of the light beams, andcorrespondingly some of the receivers detect less light intensity. Inother embodiments, the projected light is transmitted through anoptically transmissive layer above the screen surface. The projectedlight traverses the screen without exiting this layer due to totalinternal reflection. A pointer, such as a finger or a stylus, thattouches this layer, absorbs and/or scatters some of the light beams and,correspondingly, some of the receivers detect less light intensity.

In each of these embodiments, the geometry of the locations of theemitters and receivers, and the detected light intensities, determinethe screen coordinates of the pointer. The emitters and receivers arecontrolled for selective activation and de-activation by a controller.Generally, each emitter and receiver has I/O connectors, and signals aretransmitted to specify which emitters and which receivers are activated.

In an embodiment of the present invention, plural emitters are arrangedalong two adjacent sides of a rectangular screen, and plural receiversare arranged along the other two adjacent sides. In this regard,reference is now made to FIG. 10, which is a diagram of a touch screen800 having 16 emitters 200 and 16 receivers 300, in accordance with anembodiment of the present invention. Emitters 200 emit infra-red or nearinfra-red light beams across the top of the touch screen, which aredetected by corresponding receivers 300 that are directly oppositerespective emitters 200. When a pointer touches touch screen 800, itdiminishes the amount of light that reaches some of receivers 300,either by obstructing a portion of the beam, or by absorbing and/orscattering a portion of the beam as described above. By identifying,from the receiver outputs, which light beams have been blocked orreduced by the pointer, the pointer's location can be determined.

Reference is now made to FIGS. 11-13, which are diagrams of touch screen800 of FIG. 10, showing detection of two pointers, 901 and 902, thattouch the screen simultaneously, in accordance with an embodiment of thepresent invention. When two or more pointers touch the screensimultaneously, this is referred to as a “multi-touch.” Pointers 901 and902, which are touching the screen, block light from reaching some ofreceivers 300. In accordance with an embodiment of the presentinvention, the locations of pointers 901 and 902 are determined from thecrossed lines of the infra-red beams that the pointers block. Indistinction, prior art resistance-based and capacitance-based touchscreens are generally unable to detect a multi-touch.

When two or more pointers touch screen 800 simultaneously along a commonhorizontal or vertical axis, the positions of the pointers aredetermined by the receivers 300 that are blocked. Pointers 901 and 902in FIG. 11 are aligned along a common vertical axis and blocksubstantially the same receivers 300 along the bottom edge of touchscreen 800; namely the receivers marked a, b, c and d. Along the leftedge of touch screen 800, two different sets of receivers 300 areblocked. Pointer 901 blocks the receivers marked e and f, and pointer902 blocks the receivers marked g and h. The two pointers are thusdetermined to be situated at two locations. Pointer 901 has screencoordinates located at the intersection of the light beams blocked fromreceivers a-d and receivers e and f; and pointer 902 has screencoordinates located at the intersection of the light beams blocked fromreceivers a-d and receivers g and h.

Pointers 901 and 902 shown in FIGS. 12 and 13 are not aligned along acommon horizontal or vertical axis, and they have different horizontallocations and different vertical locations. From the blocked receiversa-h, it is determined that pointers 901 and 902 are diagonally oppositeone another. They are either respectively touching the top right andbottom left of touch screen 800, as illustrated in FIG. 8; or elserespectively touching the bottom right and top left of touch screen 800,as illustrated in FIG. 13.

For light-based touch screens that use total internal reflection,discriminating between FIG. 12 and FIG. 13 is resolved by analyzingincreases in light detection due to scattered light. This analysis isdescribed in detail below with reference to FIG. 122.

Determining locations of a diagonally oriented multi-touch is furtherdiscussed below with reference to shift-aligned arrangements of emittersand receivers, and with reference to light beams directed along fouraxes. An additional method of resolving ambiguous multi-touches isdescribed with reference to fast scan frequencies enabled by the ASICcontroller discussed hereinbelow.

Reference is now made to FIGS. 14 and 15, which are diagrams of a touchscreen 800 that detects a two-finger glide movement, in accordance withan embodiment of the present invention. The two-finger glide movementillustrated in FIGS. 14 and 15 is a diagonal pinch gesture that bringspointers 901 and 902 closer together. The direction of the glide isdetermined from changes in which receivers 300 are blocked. As shown inFIGS. 14 and 18, blocked receivers are changing from a and b toreceivers 300 more to the right, and from c and d to receivers 300 moreto the left. Similarly, blocked receivers are changing from e and f toreceivers 300 more to the bottom, and from g and h to receivers 300 moreto the top. For a two-finger glide in the opposite direction, i.e., aspread, or reverse-pinch, gesture, that moves pointers 901 and 902farther apart, the blocked receivers change in the opposite directions.

When pointers 901 and 902 are aligned along a common vertical orhorizontal axis, there is no ambiguity in identifying two-finger glidepatterns. When pointers 901 and 902 are not aligned in a common verticalor horizontal axis, there may be ambiguity in identifying glidepatterns, as illustrated in FIGS. 14 and 15. In case of such ambiguity,and as described hereinabove with reference to FIGS. 12 and 13,discriminating between FIG. 14 and FIG. 15 is resolved by analyzingincreases in light detection due to scattered light, as described indetail below with reference to FIG. 122.

Reference is made to FIG. 16, which is a circuit diagram of touch screen800 from FIG. 10, in accordance with an embodiment of the presentinvention. The emitters and receivers are controlled by a controller(not shown). The emitters receive respective signals LED00-LED15 fromswitches A, and receive current from VROW and VCOL through currentlimiters B. The receivers receive respective signals PD00-PD15 fromshift register 730. Receiver output is sent to the controller viasignals PDROW and PDCOL. Operation of the controller, of switches A andof current limiters B is described in applicant's co-pendingapplication, U.S. application Ser. No. 12/371,609 filed on Feb. 15,2009, now U.S. Pat. No. 8,339,379, and entitled LIGHT-BASED TOUCHSCREEN, the contents of which are hereby incorporated by reference.

According to an embodiment of the present invention, the emitters arecontrolled via a first serial interface, which transmits a binary stringto a shift register 720. Each bit of the binary string corresponds toone of the emitters, and indicates whether to activate or deactivate thecorresponding emitter, where a bit value “1” indicates activation and abit value “0” indicates deactivation. Successive emitters are activatedand deactivated by shifting the bit string within shift register 720.

Similarly, the receivers are controlled by a second serial interface,which transmits a binary string to a shift register 730. Successivereceivers are activated and deactivated by shifting the bit string inshift register 730. Operation of shift registers 720 and 730 isdescribed in U.S. application Ser. No. 12/371,609 referenced above.

Reference is made to FIG. 17, which is a simplified diagram of alight-based touch screen system, in accordance with an embodiment of thepresent invention. A first portion of the light emitted by emitter 200is directed through air above a cover glass that covers the display. Asecond portion of the light emitted by emitter 200 is directed into thecover glass. The second portion of the light is guided by total internalreflection. A small infrared transparent frame 407 surrounds the displayto reflect the first portion of light beams between emitters 200 andreceivers positioned on opposite sides of the screen. When a pointer,such as a finger or a stylus, touches the cover glass at a specific area905, one or more light beams generated by emitters 200 are obstructed;specifically, the first portion of beams are blocked by the finger, andthe second portion of beams are at least partially absorbed by thefinger. The obstructed light beams are detected by correspondingdecreases in light received by one or more of the receivers, which isused to determine the location of the pointer.

Reference is made to FIG. 18, which is a simplified cross-sectionaldiagram of the touch screen system of FIG. 17, in accordance with anembodiment of the present invention. Shown in FIG. 18 is across-sectional view of a section A-A of an LCD display 635, a coverglass 646, and its surrounding infrared transparent frame 407. Thecross-sectional view shows an emitter 200 emitting light 100 that isreflected by a cut-out 408 in frame 407, and directed substantiallyparallel over the display surface. The cross-sectional view also showsemitted light 103 that is internally reflected in cover glass 646,across the display surface. As a finger 900 approaches cover glass 646,some of the light, 101, emitted by the emitters and directed over thelocation of the near touch is blocked by the finger, and some of thelight, 102, passes between the fingertip and the cover glass. Thereduction in detected light is substantially linear as the finger drawscloser to the cover glass. The internally reflected portion of the light103 is unaffected by the approaching finger. When finger 900 touches thedisplay surface, all of the light emitted by the emitters and directedthrough air above the touch location, e.g., beams 101 and 102, isblocked by finger 900. In addition, a significant portion of theinternally reflected light 103 is absorbed and/or scattered by thefinger, causing a sudden drop in the amount of detected light when thefinger touches the cover glass. This provides an indication as to whencontact was first made.

Touch Screen System Configuration No. 1

Reference is made to FIG. 19, which is a simplified illustration of anarrangement of emitters, receivers and optical elements that enable atouch screen system to determine a precise location of a fingertiptouching the screen, in accordance with an embodiment of the presentinvention. Shown in FIG. 19 are a mirror or optical lens 400, an emitter200, a wide reflected light beam 105, a pointer 900 and a receiver 300.Mirror or optical lens 400 generates a wide light beam that is focusedonto receiver 300 by a second mirror or optical lens. The wide beammakes it possible to sense an analog change in the amount of lightdetected at receiver 300 when a pointer blocks a portion of the widebeam. In some embodiments the mirror or optical lens 400 distributeslight at approximately uniform intensity along the width of beam 105.Thus, as a fingertip passes across wide beam 105, it blocks increasingamounts of the beam, and the amount of light blocked is linearlyproportional to the width of the blocked portion of the beam. Thefingertip is slightly wider than each wide beam, such that the fingertipis detected by at least two adjacent wide beams. The precise location ofthe finger is determined by interpolating the detection signals inadjacent beams. In systems where wide beam 105 is directed through airover screen 800, pointer 900 in FIG. 19 blocks only a portion of widebeam 105. In systems where beam 105 is directed by total internalreflection through a cover glass placed above screen 800, when pointer900 touches the cover glass it absorbs and/or scatters a portion of widebeam 105. In addition to enabling precise detection of a fingertip, thewide beam also enables mounting the emitters far apart from one another,and mounting the receivers far apart from one another. Consequently,this reduces the bill of materials by requiring fewer emitters and fewerreceivers.

Reference is made to FIG. 20, which is a simplified illustration of anarrangement of emitters, receivers and optical elements that enable atouch screen system to detect a pointer that is smaller than the sensorelements, including inter alia a stylus, in accordance with anembodiment of the present invention. Shown in FIG. 20 are a mirror oroptical lens 400, an emitter 200, a wide reflected light beam, 105, apointer 900 and a receiver 300. Mirror or optical lens 400 generates awide light beam that is focused onto receiver 300 by a second mirror oroptical lens. The wide beam enables sensing of an analog change in theamount of light detected at receiver 300 when a pointer 900 blocks aportion of the wide beam, either by directly blocking the beam path whenthe beam travels through air above the display, or by absorbing aportion of the beam when the beam is guided, by total internalreflection, through a cover glass. A detailed discussion of theabsorption using a cover glass is provided below with reference toconfiguration no. 6. Pointer 900, as shown in FIG. 20, blocks only aportion of wide beam 105, indicated by beam 106 being blocked by the tipof pointer 900. In some embodiments, the mirror or optical lens 400distributes light at graduating intensities along the width of beam 105,with a weak signal at the edges linearly increasing to a maximumintensity at the center. Thus, as a stylus passes across the wide beamit blocks different amounts of the beam, and the amount of blocked lightdepends on the location of the stylus within the width of the beam. Suchembodiments are described below, with reference to FIGS. 30 and 31, inwhich beams from two emitter-receiver pairs along one axis overlap andprovide two detection signals for the stylus. This enables determinationof whether the stylus is in the right half or in the left half of thebeam. The wide beam also enables mounting emitters far apart from oneanother, and mounting receivers far apart from one another. In turn,this reduces the bill of materials by requiring fewer emitters and fewerreceivers.

Without the wide beam, there are generally spaces between beams that goundetected, making it impossible to distinguish between a user dragginga fine-point stylus across the beams, and the user tapping on differentbeams with a fine-point stylus. Moreover, with widely spaced narrowbeams the pointer touch must be very precise in order to cross a narrowbeam.

Reference is made to FIG. 21, which is a simplified diagram of a touchscreen with wide light beams covering the screen, in accordance with anembodiment of the present invention. Touch screen systems using widebeams are described in applicant's provisional patent application, U.S.Application Ser. No. 61/317,255 filed on Mar. 24, 2010 and entitledOPTICAL TOUCH SCREEN WITH WIDE BEAM TRANSMITTERS AND RECEIVERS, thecontents of which are hereby incorporated by reference.

The emitters and receivers shown in FIG. 21 are spaced relatively widelyapart. Generally, the emitters are not activated simultaneously.Instead, they are activated one after another, and the coverage areas oftheir light beams are substantially connected.

FIG. 21 shows a top view and a side view of a touch system having atouch screen or touch surface 800. The touch system providestouch-sensitive functionality to a surface irrespective of whether ornot the surface includes a display screen. Moreover, a physical surfaceis not required; the light beams may be projected though the air, andthe location of a pointer in mid-air that breaks the light beams may bedetected. In an alternative embodiment, a cover glass is used to guidethe light by total internal reflection, and a touch absorbs a portion ofthe internally reflected light. Absorption using a cover glass isdescribed in detail below with reference to configuration no. 6.

Also shown in FIG. 21 are emitters 200, reflectors 437 and 438, andreceivers 300 coupled with a calculating unit 770. Emitters 200 andreceivers 300 are positioned beneath screen 800. Emitters 200 projectarcs 142 of light under screen 800 onto reflectors 437. The distancebetween emitters 200 and reflectors 437 is sufficient for an arc tospread into a wide beam at a reflector 437. In various embodiments ofthe present invention, the distance between emitters 200 and reflectors437 may be approximately 4 mm, 10 mm, 20 mm or greater, depending onfactors including inter alia the widths of the wide beams, the requiredtouch resolution, the emitter characteristics and the optical reflectorcharacteristics.

Reflectors 437 collimate the light as wide beams 144 across a swath ofscreen surface. As explained above, in systems intended for fingertouch, it is of advantage to distribute light uniformly across the widthof the beam, whereas in systems intended for stylus touch it is ofadvantage to distribute light at different intensities across the widthof the beam. Nevertheless, systems that distribute light at differentintensities along the width of the beam may precisely determine thelocation of a finger touch based on the portion of the beam that isblocked, if the intensity distribution across the beam is known. A widebeam 144 reaches a reflector 438, which (i) redirects the light beambelow screen 800, and (ii) narrows the wide beam 144 into an arc 143. Assuch, wide beam 144 converges onto the surface of one of receivers 300below the surface of screen 800. The light intensity detected by each ofreceivers 300 is communicated to calculating unit 770.

The configuration of FIG. 21 is of advantage in that the wide lightbeams cover the entire screen surface, thereby enabling touch sensitivefunctionality anywhere on the screen. Additionally, the cost ofmaterials for the touch screen is reduced, since relatively few emitterand receiver components are required.

Touch Screen System Configuration No. 2

Configurations 2-6 use multiple emitter-receiver pairs to preciselyidentify a touch position. In some of the configurations describedhereinabove there are opposing rows of emitters and receivers, eachemitter being opposite a respective receiver. In configurations 2 and 3the emitters are shift-aligned with the receivers. For example, eachemitter may be positioned opposite a midpoint between two opposingreceivers. Alternatively, each emitter may be off-axis aligned with anopposite receiver, but not opposite the midpoint between two receivers.

Embodiments of the present invention employ two types of collimatinglenses; namely, (i) conventional collimating lenses, and (ii)collimating lenses coupled with a surface of micro-lenses that refractlight to form multiple wide divergent beams. When a light source ispositioned at the focus of a conventional collimating lens, the lensoutputs light in substantially parallel beams, as illustrated inter aliain FIGS. 19-21. When a light source is positioned between a conventionalcollimating lens and its focus, the lens outputs a wide beam, the outeredges of which are not parallel to each other, as illustrated inter aliain FIGS. 27-30.

Reference is made to FIG. 22, which is a simplified illustration of acollimating lens in cooperation with a light emitter, in accordance withan embodiment of the present invention. Shown in FIG. 22 is (A) a lightemitter 200 transmitting light beams 190 through a flat clear glass 524.Beams 190 are unaltered by the glass.

Also shown in FIG. 22 is (B) an emitter positioned at the focus of acollimating lens 525. Beams 190 are collimated by lens 525.

Also shown in FIG. 22 is (C) an emitter 200 positioned betweencollimating lens 525 and the lens' focus. Beams 190 are partiallycollimated by lens 525; i.e., the output wide beams are not completelyparallel.

Reference is made to FIG. 23, which is a simplified illustration of acollimating lens in cooperation with a light receiver, in accordancewith an embodiment of the present invention. Shown in FIG. 23 is (A)substantially parallel light beams 191 transmitted through a flat clearglass 524. Beams 191 are unaltered by the glass.

Also shown in FIG. 23 is (B) a receiver 300 positioned at the focus ofcollimating lens 525. Beams 191 are refracted onto receiver 300 bycollimating lens 525.

Also shown in FIG. 23 is (C) a receiver 300 positioned betweencollimating lens 525 and the lens' focus. Beams 191 are collimated bylens 525, but because receiver 300 is not at the lens focus, the beamsdo not converge thereon.

Collimating lenses coupled with an outer surface of micro-lenses, whichface away from emitters or receivers, transmit light in two stages. Aslight passes through the bodies of the lenses, light beams arecollimated as with conventional collimating lenses. However, as thelight passes through the surface of micro-lenses, the light is refractedinto multiple wide divergent beams, as illustrated inter alia in FIGS.34, 35 and 37-39. In FIGS. 38 and 39, collimating lenses 439 and 440 areshown having micro-lens surfaces 444. In FIG. 38, light emitters 201 and202 are positioned within the focal distance of collimating lenses 439and 440, and wide light beams from the emitters are shown enteringlenses 439 and 440. Light is collimated as it passes through the lens,as with conventional collimating lenses. When the collimated lightpasses through micro-lens surface 444, it is refracted into multiplewide divergent beams, three of which are illustrated in FIG. 38. In FIG.39, light receivers 301 and 302 are positioned within the focal distanceof the collimating lenses, and light beams are shown entering lenses 439and 440 through micro-lens surface 444. The incoming beams are refractedinto wide divergent beams inside the lens bodies. The refracted beamsare directed by the collimating portions of lenses 439 and 440, whichconcentrate the beams onto light receivers 301 and 302.

Reference is made to FIG. 24, which is a simplified illustration of acollimating lens having a surface of micro-lenses facing an emitter, inaccordance with an embodiment of the present invention. FIG. 24 shows(A) a flat glass 526 having micro-lenses etched on a surface facing anemitter 200. Light beams 190 enter glass 526 at various angles. At eachentry point, a micro-lens refracts an incoming beam into a wide arc 192.Lines 183 show how the middle of each arc is oriented in a differentdirection, depending on the angle of approach of the beam into glass526.

FIG. 24 also shows (B) a collimating lens 527 having micro-lenses etchedon a surface facing an emitter 200. A focus point of the lens, withoutthe micro-lenses, is determined, and emitter 200 is positioned at thatpoint. Light beams 190 enter collimating lens 527 at various angles. Ateach entry point, a micro-lens refracts the incoming beams into a widearc 192. Lines 184 show how the middle of each arc is oriented in thesame direction, irrespective of the angle of approach of the beams intocollimating lens 527. This type of lens is referred to as a“multi-directional collimating lens”, because it outputs arcs of light,not parallel beams, but all of the arcs are substantially uniformlydirected.

FIG. 24 also shows (C) the same collimating lens 527, but with emitter200 positioned between the lens and the focus point. The output arcs 192are oriented in directions between those of the arcs of (A) and the arcsof (B), indicated by lines 185.

Reference is made to FIG. 25, which is a simplified illustration of acollimating lens having a surface of micro-lenses facing a receiver, inaccordance with an embodiment of the present invention. FIG. 25 shows(A) a flat glass 526 having micro-lenses etched on a surface facing areceiver 300. Light beams 191 are shown entering glass 526 as parallelbeams. At each exit point, a micro-lens refracts a beam into a wide arc192. Lines 186 show how the middle of each arc is oriented in the samedirection. The arcs do not converge on receiver 300.

FIG. 25 also shows (B) a multi-directional collimating lens 527 havingmicro-lenses etched on a surface facing receiver 300. A focus point ofthe lens, without the micro-lenses, is determined, and receiver 300 ispositioned at that point. Light beams 191 enter lens 527 assubstantially parallel beams. At each exit point, a micro-lens refractsan incoming beam into a wide arc 192. Lines 187 show how the middle ofeach arc is oriented towards receiver 300.

FIG. 25 also shows (C) the same lens 527, but with receiver 300positioned between the lens and the focus point.

As used through the present specification, the term “collimating lens”includes a multi-directional collimating lens.

Reference is made to FIG. 26, which is a simplified diagram of anelectronic device with a wide-beam touch screen, in accordance with anembodiment of the present invention. Shown in FIG. 26 is an electronicdevice 826 with two emitters, 201 and 202, and three receivers, 301, 302and 303, the emitters and receivers being placed along opposite edges ofa display 636. Light intensities detected at each of receivers 301, 302and 303, are communicated to a calculating unit 770. Each emitter andreceiver uses a respective primary lens, labeled respectively 441, 442,443, 439 and 440. Emitters and receivers use the same lens arrangement,to ensure that light emitted by an emitter and re-directed by an emitterlens, is reverse-directed by an opposing lens onto a receiver.

It is desirable that the light beam from each emitter covers its twoopposite receiver lenses. Such a condition is achieved by positioningeach emitter between its lens and its lens' focal point. As such, theemitter is not in focus and, as a result, its light is spread, insteadof being collimated, by its lens. Each receiver is similarly positionedbetween its lens and its lens' focal point.

Reference is made to FIG. 27, which is a diagram of electronic device826 of FIG. 26, depicting overlapping light beams from one emitterdetected by two receivers, in accordance with an embodiment of thepresent invention. Shown in FIG. 27 are two wide light beams fromemitter 201, one of which is detected at receiver 301 and another ofwhich is detected at receiver 302, respectively. The left and rightsides of the one beam are marked 145 and 146, respectively, and the leftand right sides of the other beam are marked 147 and 148, respectively.The shaded area in FIG. 27 indicates the area on display 636 at which atouch blocks a portion of both wide beams. As such, a touch in this areais detected by two emitter-receiver pairs; namely, 201-301 and 201-302.The touch blocks a portion of both wide beams, either by directlyblocking the beam path when the beam travels through air above thedisplay, or by absorbing a portion of the beam if guided by totalinternal reflection through a cover glass. Absorption using a coverglass is described in detail below with reference to configuration no.7.

Reference is made to FIG. 28, which is a diagram of electronic device826 of FIG. 26, depicting overlapping light beams from two emittersdetected by one receiver, in accordance with an embodiment of thepresent invention. Shown in FIG. 28 are wide beams, one from emitter 201and another from emitter 202, that are both detected at receiver 302.The left and right sides of the one beam are marked 145 and 146,respectively, and the left and right sides of the other beam are marked147 and 148, respectively. The shaded area in FIG. 28 indicates the areaon display 636 at which a touch blocks a portion of both wide beams. Assuch, a touch in this area is detected by two emitter-receiver pairs;namely, 201-302 and 202-302.

Reference is now made to FIG. 29, which is a diagram of the electronicdevice 826 of FIG. 26, showing that points on the screen are detected byat least two emitter-receiver pairs, in accordance with an embodiment ofthe present invention. FIG. 29 shows the wide beams of FIGS. 27 and 28,and illustrates that touches in the shaded wedges on display 636 aredetected by at least two emitter-receiver pairs. The twoemitter-receiver pairs are either one emitter with two receivers, as inFIG. 27, or two emitters with one receiver, as in FIG. 28. Morespecifically, touches that occur near the row of emitters are generallydetected by the former, and touches that occur near the row of detectorsare generally detected by the latter. By surrounding the screen withsimilarly arranged emitters, lenses and receivers, any point may besimilarly detected by two emitter-receiver pairs.

Reference is made to FIG. 30, which is a simplified diagram of awide-beam touch screen, showing an intensity distribution of a lightsignal, in accordance with an embodiment of the present invention. Shownin FIG. 30 is a wide angle light beam emitted by emitter 201 into lens439. The light beam crosses over display 636 and substantially spanslenses 441 and 442. The light is detected at receivers 301 and 302.

Shown in FIG. 30 is a graph of detected light intensity. Total detectedlight corresponds to a shaded area under the graph. An object touchingthe screen blocks a portion of this light. If the object touching thescreen moves across the wide beam, from left to right, the amount ofblocked light increases, and correspondingly the total detected lightdecreases, as the object progresses from the left edge of the beam tothe center of the beam. Similarly, the amount of blocked lightdecreases, and correspondingly the total detected light increases, asthe object progresses from the center of the beam to the right edge ofthe beam.

It is noted that the detected light intensities at the edges of thelight beam are strictly positive, thus ensuring that a touch at theseedges is detected.

Reference is made to FIG. 31, which is a simplified diagram of awide-beam touch screen, showing intensity distributions of overlappinglight signals from two emitters, in accordance with an embodiment of thepresent invention. FIG. 31 shows light detected from emitters 201 and202. A touch point 980 on display 636 blocks light from these emittersdifferently. Area 973 indicates attenuation of light from emitter 201 bytouch point 980, and the union of areas 973 and 974 corresponds to theattenuation of light from emitter 202 by point 980. By comparing thelight attenuation the two emitter-receiver pairs, 201-302 and 202-302, aprecise touch coordinate is determined.

Reference is made to FIG. 32, which is a simplified diagram of awide-beam touch screen, showing intensity distributions of two sets ofoverlapping light signals from one emitter, in accordance with anembodiment of the present invention. As shown in FIG. 32, touch point980 is inside the area detected by emitter-receiver pair 201-301 andemitter-receiver pair 201-302. The attenuation of the light signal atreceiver 302, depicted as area 976, is greater than the attenuation atreceiver 301, depicted as area 975. By comparing the light attenuationin the two emitter-receiver pairs, 201-301 and 201-302, a precise touchcoordinate is determined.

Determining the position of touch point 980 requires determining aposition along an axis parallel to the edge along which the emitters arepositioned, say, the x-axis, and along an axis perpendicular to theedge, say, the y-axis. In accordance with an embodiment of the presentinvention, an approximate y-coordinate is first determined and then,based on the expected attenuation values for a point having the thusdetermined y-coordinate and based on the actual attenuation values, aprecise x-coordinate is determined. In turn, the x-coordinate thusdetermined is used to determine a precise y-coordinate. In cases wherethe touch point 980 is already touching the screen, either stationary orin motion, previous x and y coordinates of the touch point are used asapproximations to subsequent x and y coordinates. Alternatively, onlyone previous coordinate is used to calculate a first subsequentcoordinate, with the second subsequent coordinate being calculated basedon the first subsequent coordinate. Alternatively, previous coordinatesare not used.

Reference is made to FIG. 33, which is a simplified diagram of awide-beam touch screen with emitter and receiver lenses that do not havemicro-lens patterns, in accordance with an embodiment of the presentinvention. Shown in FIG. 33 is an electronic device 826 with a display636, emitters 201 and 202, corresponding emitter lenses 439 and 440,receivers 301, 302 and 303, and corresponding receiver lenses 441, 442and 443. Two light beams, 151 and 152, from respective emitters 201 and202, arrive at a point 977 that is located at an outer edge of lens 442.Since beams 151 and 152 approach point 977 at different angles ofincidence, they do not converge on receiver 302. Specifically, lightbeam 152 arrives at receiver 302, and light beam 151 does not arrive atreceiver 302.

In order to remedy the non-convergence, a fine pattern of micro-lensesis integrated with the receiver lenses, at many points long the surfacesof the lenses. The micro-lenses distribute incoming light so that aportion of the light arriving at each micro-lens reaches the receivers.In this regard, reference is made to FIGS. 34 and 35, which aresimplified diagrams of a wide-beam touch screen with emitter anddetector lenses that have micro-lens patterns, in accordance with anembodiment of the present invention. FIG. 34 shows incoming beam 151being spread across an angle θ by a micro-lens at location 977, thusensuring that a portion of the beam reaches receiver 302. FIG. 35 showsincoming beam 152 being spread across an angle ψ by the same micro-lensat location 977, thus ensuring that a portion of this beam, too, reachesreceiver 302. By arranging the micro-lenses at many locations along eachreceiver lens, light beams that enter the locations from differentangles are all detected by the receiver. The detected light intensitiesare communicated to a calculating unit 770 coupled with the receivers.

Reference is made to FIG. 36, which is a simplified diagram of awide-beam touch screen with emitter and receiver lenses that do not havemicro-lens patterns, in accordance with an embodiment of the presentinvention. Shown in FIG. 36 is an electronic device 826 with a display636, emitters 201 and 202, corresponding emitter lenses 439 and 440,receivers 301, 302 and 303, and corresponding receiver lenses 441, 442and 443. Two light beams emitted by emitter 201 and detected byrespective receivers 301 and 302, are desired in order to determine aprecise location of touch point 980. However, lens 439, withoutmicro-lens patterns, cannot refract a beam crossing point 980 toreceiver 301. I.e., referring to FIG. 36, lens 439 cannot refract beam153 as shown. Only the beam shown as 154, crossing point 980, isdetected.

In order to remedy this detection problem, micro-lenses are integratedwith the emitter lenses at many points along the surface of the lenses.The micro-lenses distribute outgoing light so that a portion of thelight reaches the desired receivers. In this regard, reference is madeto FIG. 37, which is a simplified diagram of a wide beam touch screen,with emitter and receiver lenses that have micro-lens patterns, inaccordance with an embodiment of the present invention. FIG. 37 showsthat a portion of light exiting from micro-lens location 982 reachesmultiple receivers. As such, a touch at point 980 is detected byreceivers 301 and 302. It will be noted from FIGS. 36 and 37 that thebeams passing through point 980 are generated by micro-lenses atdifferent locations 981 and 982. Light intensity values detected by thereceivers of FIGS. 36 and 37 are communicated to a calculating unit 770.

Micro-lens patterns integrated with emitter and receiver lenses thusgenerate numerous overlapping light beams that are detected. Each pointon the touch screen is traversed by multiple light beams from multiplemicro-lenses, which may be on the same emitter lens. The micro-lensesensure that the multiple light beams reach the desired receivers.Reference is made to FIG. 38, which is a simplified diagram of twoemitters, 201 and 202, with respective lenses, 439 and 440, that havemicro-lens patterns 444 integrated therein, in accordance with anembodiment of the present invention. Reference is also made to FIG. 39,which is a simplified diagram of two receivers, 301 and 302, withrespective lenses, 439 and 440, that have micro-lens patterns 444integrated therein, in accordance with an embodiment of the presentinvention.

When the light beams are guided across the screen through a cover glassby total internal reflection, as described below with reference toconfiguration no. 7, the lenses are not exposed to the user. However,when the light beams are directed above the screen through air, theoutermost surfaces of the lenses are visible to the user, and it may beless aesthetic to have the micro-lenses on these exposed surfaces, inorder that the visible surfaces appear smooth. Moreover, outermostsurfaces are susceptible to scratching and to accumulation of dust anddirt, which can degrade performance of the micro-lenses. As such, inembodiments of the present invention, the micro-lenses are integrated onsurfaces that are not exposed to the user, as shown below in FIGS. 40,41 and 44. Although these lenses have particular advantages forthrough-air beams, the lenses described in FIGS. 40, 41 and 44 may alsobe connected to a cover glass and used when light beams are guidedacross the screen through the cover glass by total internal reflection.

Reference is made to FIG. 40, which is a simplified diagram of a sideview of a single-unit light guide, in the context of an electronicdevice having a display and an outer casing, in accordance with anembodiment of the present invention. Shown in FIG. 40 is a cut-away of aportion of an electronic device with a display screen 637, an outercasing 827 above screen 637, and an emitter 200 below screen 637. Alight guide 450 receives light beams 100 and reflects them above screen637 so that they travel across the surface of screen 637 for detection.Light guide 450 includes internal reflective surfaces 451 and 452 forprojecting light beams 100 above the surface of screen 637. A section445 of light guide 450 serves as a primary lens to collimate light beams100 when they are received. The surface of section 445 that facesemitter 200, indicated in bold, has patterns of micro-lenses etchedthereon. As such, the micro-lenses are not visible to a user, and areprotected from damage and dirt.

The surface of section 445 has a feather pattern for scattering incominglight beams 100 from an emitter 200. Reflective surfaces 451 and 452reflect light beams 100. Reflective surface 451 is concave, andreflective surface 452 is a flat reflector oriented at a 45° angle withrespect to incoming light beams 100.

Light beams 100 exit light guide 450 through flat surface 453. Surface454 serves to connect light guide 450 to outer casing 827. Surface 454is located above the plane of active light beams used by the touchsystem, and is angled for aesthetic purposes.

The reflective characteristics of surface 452 require that dust and dirtnot accumulate on surface 452, and require that outer casing 827, whichmay be made inter glia of metal or plastic, not make contact withsurface 452; otherwise, reflectivity of surface 452 may be impaired. Assuch, outer casing 827 is placed above surface 452, thereby protectingsurface 452 from dust and dirt, and outer casing 827 is not flush withsurface 452, so that casing material does not touch surface 452. Being aflat reflector at a 45° angle relative to incoming light beams, surface452 is positioned above the upper surface of display 637. As such, thedevice height, H3, above display 637 due to light guide 450, comprisesthe height, H1, of surface 452 plus the thickness, H2, of outer casing827.

At the receiving side, a light guide similar to 450 is used to receivelight beams 100 that are transmitted over screen 637, and to direct themonto corresponding one or more receivers. Thus, light beams enter lightguide 450 at surface 453, are re-directed by surface 452 and then bysurface 451, and exit through the micro-lens patterned surface ofsection 445 to one or more receivers. At the receiving side, the surfaceof section 445 has a pattern that scatters the light beams as describedhereinabove.

Reference is made to FIG. 41, which is a simplified diagram of sideviews, from two different angles, of a lens with applied featherpatterns on a surface, in accordance with an embodiment of the presentinvention. Shown in FIG. 41 is a light guide 455 having an internalreflective section 456, an internal collimating lens 457, and etchedmicro-lenses 458. Light beams 101 entering light guide 455 at lens 457exit the light guide through a surface 459 as light beams 105.

Similar light guides are used for receiving beams that have traversedthe screen, to focus them onto receivers. In this case, light beamsenter at surface 459, are reflected below the screen surface by internalreflective section 456, are re-focused onto a receiver by collimatinglens 457, and re-distributed by micro-lenses 458. In general, the samelens and micro-lenses are used with an emitter and a detector, in orderthat the light beam be directed at the receiving side in reverse to theway it is directed at the emitting side.

Collimating lens 457 has a rounded bottom edge, as shown at the bottomof FIG. 41. In order to properly refract incoming light on the emitterside, the micro-lenses 458 are formed in a feather pattern, spreading asa fan, as shown at the bottom of FIG. 41 and in FIG. 42.

Reference is made to FIG. 42, which is a simplified diagram of a portionof a wide-beam touch screen, in accordance with an embodiment of thepresent invention. A feather pattern 460 is shown applied to the surfaceof a lens 461. A similar neighboring lens is associated with an emitter200 emitting a wide beam 158.

Reference is made to FIG. 43, which is a top view of light beamsentering and exiting micro-lenses etched on a lens, in accordance withan embodiment of the present invention. Substantially collimated lightbeams 101 are shown in FIG. 43 entering micro-lenses 462 and beingrefracted to light beams 102, such that each micro-lens acts as a lightsource spreading a wide beam across a wide angle.

Touch Screen System Configuration No. 3

Several challenges arise in the manufacture of the micro-lenses inconfiguration no. 2. One challenge is the difficulty of accuratelyforming the fan-shaped feather pattern of micro-lenses. It is desirableinstead to use micro-lenses arranged parallel to one another, instead ofthe fan/feather pattern.

A second challenge relates to the mold used to manufacture the lightguide in configuration no. 2. Referring to FIG. 40, it is desirable thatthe outer surface of section 445, facing emitter 200, be vertical, sothat the front surface of section 445 is parallel with the straight backsurface portion of light guide 450. However, it is difficult tomanufacture exactly parallel surfaces. Moreover, if the light guide 450were to be wider at its bottom, then it would not be easily removablefrom its mold. As such, the two surfaces generally form a wedge, and thesurface of section 445 facing emitter 200 is not perfectly vertical. Tocompensate for this, the micro-lenses are arranged so as to beperpendicular to a plane of incoming light beams.

A third challenge is the constraint that, for optimal performance, themicro-lenses be positioned accurately relative to their correspondingemitter or receiver. The tolerance for such positioning is low. As such,it is desirable to separate section 445 of the light guide so that itmay be positioned accurately, and to allow more tolerance for theremaining portions of the light guide as may be required during assemblyor required for robustness to movement due to trauma of the electronicdevice.

Configuration no. 3, as illustrated in FIGS. 44-46 and 54, serves toovercome these, and other, challenges.

Reference is made to FIG. 44, which is a simplified diagram of a sideview of a dual-unit guide, in the context of an electronic device havinga display 637 and an outer casing 827, in accordance with an embodimentof the present invention. Shown in FIG. 44 is an arrangement similar tothat of FIG. 40, but with light guide 450 split into an upper portion463 and a lower portion 464. The micro-lenses are located at an uppersurface 466 of lower portion 464. As such, the micro-lenses are notembedded in the collimating lens portion of light guide 464.

In configuration no. 2, the curved shape of the collimating lensnecessitated a fan/feather pattern for the micro-lenses etched thereon.In distinction, in configuration no. 3 the micro-lenses are etched onrectangular surface 466, and are arranged as parallel rows. Such aparallel arrangement, referred to herein as a “tubular arrangement”, isshown in FIG. 46. Specifically, a parallel series of micro-lenses 467are shown along an upper surface of light guide 464 in FIG. 46.

An advantage of configuration no. 3 is that the flat upper surface ofthe light guide may be molded as nearly parallel with the screen surfaceas possible, since the mold is one flat surface that lifts off the topof light guide 464. Furthermore, in configuration no. 3, only portion464 of the light guide has a low tolerance requirement for positioning.Portion 463 has a higher tolerance, since its surfaces are not placed ata focal point of an element.

As shown in FIG. 44, light beams 100 emitted by emitter 200 enter lightguide unit 464 at surface 465, are reflected by reflective surface 451through surface 466, and into light guide unit 463. Inside light guideunit 463, light beams 100 are reflected by surface 452, and exit throughsurface 453 over display 637.

FIG. 44 indicates that the height, H3, added by the light guide overdisplay 637 comprises the sum of the height, H1, of internal reflectivesurface 452, and the height, H2, of the thickness of outer casing 827.

Reference is made to FIG. 45, which is a picture of light guide units463 and 464, within the context of a device having a PCB 700 and anouter casing 827, in accordance with an embodiment of the presentinvention. The tubular pattern on the upper surface of light guide unit464 is a fine pattern. In order for this pattern to distribute the lightbeams correctly, light guide 464 is placed precisely relative to itsrespective LED or PD. By contrast, light guide unit 463 has a flatreflective surface and, as such, does not require such precisionplacement. FIG. 45 indicates the relative positioning of light guideunits 463 and 464. Their alignment is represented by a distance 523, andhas a tolerance of up to 1 mm. A distance 522 represents the heightbetween the light guide units.

Reference is made to FIG. 46, which is a top view of light guide units463 and 464 of FIG. 45, in accordance with an embodiment of the presentinvention. Tubular pattern 467 appears on the upper surface of lightguide unit 464.

Touch Screen System Configuration No. 4

Configuration nos. 2 and 3 relate to detection of a small touch area 980in FIGS. 31, 32, 36 and 37. A typical use case for such touch area sizeis stylus input. However when the expected use generates a relativelylarge touch area, such as the area of a fingertip, a precise touchlocation may be determined without the micro-lenses used inconfigurations 2 and 3.

Reference is made to FIG. 47, which is a simplified diagram ofshift-aligned emitters and detectors for a light-based touch screen, fordetecting finger touches, in accordance with an embodiment of thepresent invention. FIG. 47 shows a system intended for finger touch.Light from an emitter 210 is distributed uniformly across the wide beamthat spans lenses 441 and 442. Aside from the uniform distribution oflight, the system of FIG. 47 is the same as the system of FIG. 30.

Reference is made to FIG. 48, which is a simplified illustration offinger touch detection on the screen of FIG. 47, in accordance with anembodiment of the present invention. FIG. 48 shows a large touch object980 detected by two detection channels, 201-301 and 201-302. Light fromemitter 201 is substantially collimated, such that the left half of thebeam from emitter 201 reaches detector 301, and the right half of thebeam from emitter 201 reaches detector 302. A significant portion ofeach channel is blocked by pointer 980. The amount of light blocked fromeach detector is shown as portions 975 and 976. The center of theblocking pointer 980 is determined by interpolating these two amounts.In addition, because neighboring light beams 201-301 and 201-302 detectthe touch, pointer 980 lies on the border between these two beams. Thus,the leftmost edge of pointer 980 is determined based on the portion ofbeam 201-301 that is blocked. Similarly, the rightmost edge of pointer980 is determined based on the portion of beam 201-302 that is blocked.As such, the segment, or in two dimensions—the area, covered by thepointer is determined.

Touch Screen System Configuration No. 5

Configuration no. 5 uses a reflective light guide and lens that reducethe height of a light guide above a display. The reflective light guideand lens of configuration no. 5 are suitable for use with the featherpattern lenses of configuration no. 2, with the tubular pattern lensesof configuration no. 3, with the collimating lenses of configuration no.4, and also with the alternating reflective facets of configuration no.6. Many electronic devices are designed with a display surface that isflush with the edges of the devices. This is often an aesthetic featureand, as such, when integrating light-based touch screens with electronicdevices, it is desirable to minimize or eliminate the raised rims. Lessvisibly prominent rims result in sleeker, more flush outer surfaces ofthe devices.

Moreover, in light-based touch screens, the raised rim occupies a widtharound the display, beyond the edges of the display. Many electronicdevices are designed with display surfaces that seamlessly extend to theedges of the devices. This is often an aesthetic feature and, as such,when integrating light-based touch screens with electronic devices, itis desirable to design the reflective raised rims in such a way thatthey appear as seamless extensions of the display.

Configuration no. 5 achieves these objectives when light beams areprojected over air above the touch surface, by reducing bezel height andproviding a seamless transition between a display edge and an outerborder of a device, resulting in a more appealing aesthetic design. Thelight guide of configuration no. 5 integrates with an outer casinghaving an elongated rounded edge, thereby softening sharp angles andstraight surfaces.

Configuration no. 5 employs two active mirror surfaces; namely, aparabolic reflective surface that folds and focuses incoming light to afocal location, and an elliptical refractive surface that collects lightfrom the focal location and collimates the light into beams across thescreen.

Reference is made to FIG. 49, which is a simplified diagram of a sideview of a light guide within an electronic device, in accordance with anembodiment of the present invention. Shown in FIG. 49 is a light guide468 between an outer casing 828 and a display 637. Light beams from anemitter 200 enter light guide 468 through a surface 445. A featherpattern of micro-lenses is present on a lower portion of surface 445, inorder to scatter the light beams 100. Light beams 100 are reflected byan internal concave reflective surface 469 and by a parabolic reflectivesurface 470, and exit light guide 468 through an elliptical refractivesurface 471. Elliptical refractive surface 471 redirects at least aportion of light beams 100 in a plane parallel with the surface ofdisplay 637. Light beams 100 are received at the other end of display637, by a similar light guide that directs the beams onto a lightreceiver 300. The light intensity detected by light receiver 300 iscommunicated to a calculating unit 770.

Reference is made to FIG. 50, which is a simplified diagram of a sideview cutaway of a portion of an electronic device and an upper portionof a light guide with at least two active surfaces for folding lightbeams, in accordance with an embodiment of the present invention. Shownin FIG. 50 is an upper portion of a light guide 472. Surface 473 is partof a parabola, or quasi-parabola, or alternatively is a free form,having a focal line 475. Focal line 475, and surfaces 473 and 474 extendalong the rim of display 637. Surface 474 is part of an ellipse, orquasi-ellipse, or alternatively a free form, having focal line 475.

On the emitter side, light beams enter the light guide, and parabolicmirror 473 reflects the beams to a focal point inside the light guide.Refracting elliptical lens 474 has the same focal point as parabolicmirror 473. Elliptical lens 474 refracts the light from the focal pointinto collimated light beams over display 637. On the receiver side,collimated light beams enter the light guide, and are refracted byelliptical lens 474 into a focal point. Parabolic mirror 473 reflectsthe beams from the focal point inside the light guide, to collimatedoutput beams.

Surface 469 in FIG. 49 folds light beams 100 upwards by 90°. Surface 469is formed as part of a parabola. In one embodiment of the presentinvention, surface 469 is corrected for aberrations due to input surface445 being slightly inclined rather than perfectly vertical, and also dueto the light source being wider than a single point.

Surfaces 469 and 470 use internal reflections to fold light beams. Thusthese surfaces need to be protected from dirt and scratches. In FIG. 50,surface 473 is protected by outer casing 829. The lower portion (nowshown) of light guide 472 is deep within the electronic device, and isthus protected.

Using configuration no. 5, substantially all of reflective surface 473is located below the upper surface of display 637. Thus, thisconfiguration adds less height to an electronic device than doesconfiguration no. 2, when projecting light beams through the air abovethe touch surface. Referring back to FIG. 49, the height, H3′, added bythe light guide in the present configuration is approximately thethickness, H2, of the outer casing, which is less than the correspondingheight, H3, in configuration no. 2. Moreover, the convex shape ofsurface 471 of FIG. 40 and surface 474 of FIG. 50 is easier for a userto clean than is the perpendicular surface 453 of FIG. 40. Thus a usercan easily wipe away dust and dirt that may accumulate on display 637and on surface 471. It is noted that configuration no. 5 eliminates theneed for surface 454 of FIG. 40, since outer casing 828 is flush withthe height of surface 471, instead of being above it.

The convex shape of surface 471 of FIG. 49 makes the bezel less visiblyprominent than does the perpendicular surface 453 of FIG. 40.

Some electronic devices are covered with a flat sheet of glass thatextends to the four edges of the device. The underside of the glass ispainted black near the devices edges, and the display is viewed througha clear rectangular window in the middle of the glass. Examples of suchdevices include the IPHONE®, IPOD TOUCH® and IPAD®, manufactured byApple Inc. of Cupertino, Calif., and also various models of flat-panelcomputer monitors and televisions. In some cases, the light guidessurrounding the various touch screens described herein may appearnon-aesthetic, due to (a) the light guide being a separate unit from thescreen glass and thus the border between them is noticeable, and (b) thelight guide extending below the screen and thus, even if the undersideof the light guide is also painted black, the difference in heightsbetween the bottom of the light guide and the screen glass isnoticeable. Embodiments of the present invention employ a two-unit lightguide to overcome this problem.

In one such embodiment, the upper unit of the light guide is merged withthe screen glass. In this regard, reference is made to FIG. 51, which isa simplified drawing of a section of a transparent optical touch lightguide 476, formed as an integral part of a protective glass 638 coveringa display 637, in accordance with an embodiment of the presentinvention. A daylight filter sheet 639 on the underside of protectiveglass 638 serves, instead of black paint, to hide the edge of display637, without blocking light beams 100. Light guide 476 has an outerelliptical surface 478 and an inner parabolic surface 477, and mergessmoothly with an outer casing 830. Light beams 100 pass through lightguide 476 as in FIG. 50.

In some cases, the cost of manufacturing a protective glass cover withan integrated reflective lens may be expensive. As such, in analternative embodiment of the present invention, a black object isplaced between the upper and lower units of the light guide. The heightof the black object is aligned, within the electronic device, with theheight of the black paint on the underside of the protective glass. Inthis regard, reference is made to FIG. 52, which is a simplifiedillustration of the electronic device and light guide of FIG. 50,adapted to conceal the edge of the screen, in accordance with anembodiment of the present invention. Shown in FIG. 52 is black paint, oralternatively a daylight filter sheet 641, on the underside ofprotective glass 640, covering display 637. A black plastic element 482is aligned with black paint/daylight filter sheet 641, so that the edgeof protective glass 640 is not discernable by a user. Black plasticelement 482 transmits infra-red light to allow light beams 100 to passthrough.

Reference is made to FIG. 53, which is a simplified diagram of a lightguide 483 that is a single unit extending from opposite an emitter 200to above a display 637, in accordance with an embodiment of the presentinvention. A portion of an outer casing 832 is shown flush with the topof light guide 483. The lower portion of light guide 483 has a featherpattern of micro-lenses 484 to scatter the light beams arriving fromemitter 200. At the receiving side, the light beams exit through thebottom of a light guide similar to light guide 483, towards a receiver.The same feather pattern 484 breaks up the light beams en route to thereceiver.

Reference is made to FIG. 54, which is a simplified diagram of adual-unit light guide, in accordance with an embodiment of the presentinvention. Shown in FIG. 54 is a light guide with an upper unit 485 anda lower unit 486. A portion of an outer casing 832 is flush with the topof light guide unit 485. A display 637 is shown to the right of lightguide unit 485. The top surface of light guide unit 486 has a tubularpattern of micro-lenses 487 to break up light beams arriving from anemitter 200. At the receiving side, the light beams exit through thebottom of a light guide similar to the light guide shown in FIG. 54,towards a receiver. The same tubular pattern 487 breaks up the lightbeams en route to the receiver.

As explained hereinabove with reference to FIGS. 40 and 49, thepositioning of light guide unit 486 with tubular pattern 487 requireshigh precision, whereas the positioning of light guide unit 485 does notrequire such precision. The effect of tubular pattern 487 on the lightbeams depends on its precise placement relative to its respectiveemitter or receiver. The active surfaces in light guide unit 485 aremore tolerant, since they are largely self-contained; namely, they areboth focused on an internal focal line, such as focal line 475 of FIG.50.

It is noted that placement of emitters and receivers underneath a devicescreen, and placement of a collimating reflective element opposite eachemitter or receiver, imposes restrictions on the thickness of thedevice. A first restriction is that the thickness of the device be atleast the sum of the screen thickness and the emitter or receiverthickness. A second restriction is that in order to properly collimatelight that is reflected upward above the screen, the reflective elementopposite the emitter or receiver be curved into a convex “smile” shape,as shown inter alia in FIGS. 41 and 42. The convex shape adds to thetotal thickness of the device.

Designers of tablets and e-book readers strive to achieve as slim a formfactor as possible. As such, according to an embodiment of the presentinvention, the receivers and collimating lenses are placed inside aborder surrounding the screen, instead of being placed underneath thescreen. This is particularly feasible for tablets and e-book readersthat provide a non-screen border area for holding the device.

Reference is made to FIG. 55, which is a simplified diagram of a touchscreen device held by a user, in accordance with an embodiment of thepresent invention. Shown in FIG. 55 is a device 826 with a touch screen800 surrounded by a frame 840 held by hands 930.

Reference is made to FIG. 56, which is a simplified diagram of a touchscreen with wide light beams covering the screen, in accordance with anembodiment of the present invention. FIG. 56 shows a top view and a sideview of a touch system with a touch screen 800, in the context of anelectronic device such as a tablet or an e-book reader. FIG. 56 alsoshows emitters 200 and receivers 300, each coupled with a pair of lenses550 and 551, separated by an air gap 555, for collimating light. Theside view shows a device casing 827 and a frame 849 surrounding touchscreen 800. Frame 849 provides a grip for a user to hold the device, andis wide enough to encase elements 200, 300, 550 and 551.

Light is more efficiently collimated over a short distance usingmultiple air-to-plastic interfaces than with a solid lens. The emitter,receiver and lenses are substantially coplanar with the surface of touchscreen 800. The flat non-curved profile of lenses 500 and 551 along theheight of the device is lower than the profile of the lenses of FIGS. 41and 38, due to the fact that in the case of lenses 500 and 551 light isprojected only along the plane of the screen surface. The only heightadded to the device form factor is the height of the bezel, or lens 551,above touch screen 800 for directing light across the screen. Ifmicro-lens patterns are used, e.g., to create overlapping beams, then athird lens is added that includes the micro-lens patterns.Alternatively, the micro-lens patterns may be formed on one of the twolenses 500 and 551.

Reference is made to FIGS. 57-59, which are respective simplified side,top and bottom views of a light guide in the context of a device, inaccordance with an embodiment of the present invention. FIG. 57 is aside view showing a display 635 and a side-facing emitter 200 that issubstantially coplanar with display 635. A multi-lens assembly reflectslight above display 635 and outputs a wide beam. FIG. 57 shows themulti-lens assembly with three sections 550-552 separated by air gaps555 and 556. Sections 550 and 551 are connected beneath air gap 555 andform part of a rigid frame that surrounds display 635. The frameincludes a cavity 220 for accommodating side-facing emitter 200 or asimilar shaped receiver. Lens sections 550 and 551 together produce awide collimated beam as described hereinabove. Lens section 552 includesa tubular pattern of micro-lenses as described hereinabove withreference to FIGS. 45 and 46. FIG. 57 shows rays of a beam 105 crossingabove display 635. A PCB 700 forms a substrate for supporting emitters200, display 635, and the light guide frame.

FIG. 58 is a top view showing lens sections 550-552 separated by airgaps 555 and 556. FIG. 58 shows three collimated beams 105, toillustrate how lens sections 550 and 551 collimate a wide light beam.FIG. 58 also shows small connectors 559 that connect lens section 552 tothe rigid frame formed by lens sections 550 and 551. As such, all threesections 550-552 may be formed from a single piece of plastic.

FIG. 59 is a bottom view showing lens section 500 with emitter/receivercavities 220 containing three emitters 200.

Touch Screen System Configuration No. 6

In accordance with an embodiment of the present invention, highresolution touch sensitivity is achieved by combining two or moreemitter-receiver pair signals that span a common area, as describedhereinabove with reference to configurations nos. 2 and 3. Configurationno. 6 provides alternative optical elements and alternative arrangementsof emitters and receivers for providing overlapping detection.

Various approaches may be used to provide overlapping detection beams.One approach is to provide two separate wide beams that are projected atslightly different heights across the screen. Both beams cover a commonscreen area, and thus provide multiple detection signals for touches inthat area. Another approach is to provide optical elements thatinterleave rays of two wide beams when both beams are activated at once,which can be achieved using diffractive structures to interleave minuterays from two beams, or using slightly larger alternating facets tointerleave beams on the order of 0.1-0.6 mm from two sources. Generally,the two beams are activated separately. As such, they cover a commonscreen area but are not actually interleaved. This latter alternative isdescribed in what follows.

Reference is made to FIG. 60, which is a simplified illustration of atouch screen 800 surrounded by emitters and receivers, in accordancewith an embodiment of the present invention. Reference is also made toFIG. 61, which is a simplified illustration of an optical element 530with an undulating angular pattern of reflective facets, shown fromthree angles, in accordance with an embodiment of the present invention.Shown in FIG. 61 are three views, (a), (b) and (c), of optical element530. Light from the emitters enters optical element 530 as wide angledoverlapping beams. FIG. 61 shows emitters 200-202 facing a surface 541of element 530. Wide beams 107-109 from respective emitters 200-202enter element 530 through surface 541. FIG. 61 also shows the distance,or pitch, between neighboring emitter elements.

Each of wide beams 107-109 spans two pitches and, as such, the widebeams overlap in the area between neighboring emitters. A surface 542 ofelement 530 is formed as a wave-like pattern of facets, alternatinglydirected at neighboring emitters. FIG. 61(c) shows alternating shadedand non-shaded facets on surface 542. In element 530 between emitters200 and 201, shaded facets aimed at emitter 200 are interleaved withnon-shaded facets aimed at emitter 201. In element 530 between emitters201 and 202, shaded facets aimed at emitter 202 are interleaved withnon-shaded facets aimed at emitter 201.

Reference is made to FIG. 62, which is a simplified illustration of anoptical element reflecting, collimating and interleaving light from twoneighboring emitters, in accordance with an embodiment of the presentinvention. As shown in FIG. 62, each reflective facet of element 530collimates rays from its corresponding emitter, thereby interleavingcollimated rays from two emitters. FIG. 62 shows optical element 530reflecting and collimating light from two neighboring emitters 200 and201. Alternating facets of element 530 focus on these two elements. Byinterleaving collimated rays, element 530 collimates light from twoemitters across the screen in overlapping wide beams. Elements 530 at anopposite screen edge direct the wide beams onto respective receivers.

Each facet on surface 542 is precisely angled to focus on its element.The surface areas of each facet are also configured so that sufficientamounts of light are provided for detection.

Alternative embodiments of optical element 530 collimate and interleaveincoming wide beams through refraction instead of reflection. In suchcase, the wave-like multi-faceted surface is situated at an input oroutput surface of optical element 530. In the case of reflecting facets,the facets re-direct light inside the optical element.

At times, it is desirable to run a touch screen in a low frequency mode,e.g., in order to save power. Configuration no. 6 enables an accuratelow-frequency scan mode. In accordance with an embodiment of the presentinvention, two detection signals along a screen axis are provided foreach touch location. In low frequency mode, during a first scan everyother emitter-receiver pair is activated, thus activating only half ofthe pairs along only one screen axis, but nevertheless covering theentire screen. During a second scan, the remaining emitter-receiverpairs along this axis are activated. As such, odd emitter-receive pairsare first activated, then even emitter-receiver pairs, thus providingtwo full screen scans and spreading usage evenly across all emitter andreceiver elements. In order to keep power consumption at a minimum, onlyemitter-receiver pairs along the shorter edge of a rectangular screenare activated.

In an alternative embodiment of the present invention both axes of ascreen are scanned, and each scanned axis provides initial touchinformation about the screen. As such, instead of sequentiallyactivating multiple scans of a single axis, in the alternativeembodiment sequential activation of scans of separate axes areactivated. A sequence of four scans are activated at four samplingintervals; namely, (i) a first half of the emitter-receiver pairs alonga first screen axis are scanned; (ii) a first half of theemitter-receiver pairs along a second screen axis are activated, (iii)the second half of the emitter-receiver pairs along the first screenaxis are activated, and (iv) the second half of the emitter-receiverpairs along the second screen axis are activated.

Design of Reflective Elements

A goal in designing alternating reflective or refractive facets of anoptical element, is to generate a light distribution that provides goodgradients as a basis for interpolation, by way of a linear signalgradient, S(x), from an emitter to a receiver. A number of parametersaffect the light distribution.

Reference is made to FIG. 63, which is a simplified diagram of amulti-faceted optical element 530, in accordance with an embodiment ofthe present invention. Shown in FIG. 63 are parameters that controllight from each facet of the optical element, as described in whatfollows.

The light intensity distribution depends on a polar angle, θ, inaccordance with the third power, cos³ θ. The angle θ is a function ofdistance 110 between beams of a single emitter or receiver element thatgo to different facets, and of distance 111 between the emitter orreceiver element and element 530.

The facet width, B, is a readily adjustable parameter.

The Fresnel loss, F, is the amount of light lost due to reflectioncaused by the refractive index of element 530, when a beam entersoptical element 530. Variation of Fresnel loss F between differentangles θ under Brewster's angle is less than 1%, and is thereforenegligible.

Facet beam width, Y, is the total width covered by a single facet beam.The alternating facets generate gaps in the light from emitter 201, asneighboring facets are focused on neighboring emitter 202. Light fromeach facet covers the gaps. Facet beam width, Y, depends on facet widthB and on the widths of neighboring facets. FIG. 63 shows facets 545, 547and 549 aimed at emitter 201 and respective facet-beam widths Y₅₄₅, Y₅₄₇and Y₅₄₉ that together cover the neighboring facets 548 and 546 aimed atemitter 202.

Reference is made to FIG. 64, which is a simplified graph showing theeffect of reflective facet parameters θ, Y and B on light distributionfor nine facets, in accordance with an embodiment of the presentinvention. The graph of FIG. 64 also shows actual light distribution,and a reference linear function. As seen in FIG. 64, the actual lightdistribution signal is approximately linear. The data in the graph isnormalized based on the central facet, located at location 0 on thex-axis, being assigned a value of 1 in all aspects. As such, the facetwidth B is labeled Bnorm in the graph, and facet widths are normalizedrelative to the width of the central facet. Generally, the angularparameter θ provides a sloped curve, which is flat for small values ofθ, as seen in FIG. 64 in the flat portion of the θ curve, labeled cos 3,between positions 0 and 2 along the x-axis. The gradient for small θ isincreased by adjusting parameter B, which in turn affects parameter Y,labeled Yfactor. The complete signal is labeled signal in the graph, andit is approximately linear.

Light intensity for facet k, as a function of parameters θ, B, F and Y,is described in accordance with

$\begin{matrix}{{{\frac{S_{k}}{S_{1}} = {\frac{\cos^{3}\left( \theta_{k} \right)}{\cos^{3}\left( \theta_{1} \right)} \cdot \frac{B_{k}}{B_{1}} \cdot \frac{F_{k}}{F_{1}} \cdot \frac{Y_{k}}{Y_{1}}}},}\;} & (1)\end{matrix}$where the lighting of facet k is normalized based on θ=0 for the centralfacet.

TABLE I lists parameters for each facet in a series of nine facets thatare focused on one emitter or receiver element. In TABLE I, x-posdenotes the distance in millimeters from the central facet, B denotesthe facet width in millimeters, B-norm denotes the normalized facetwidth, based on the central facet having a width of 1, Yfactor denotesthe facet beam width, normalized to the width of the central facet beam,Signal denotes the normalized signal value for each facet, and Linedenotes signal values for a reference straight line.

TABLE I Facet parameters for nine facets Facet no. x-pos B B-normYfactor cos³θ Signal Line 1 0 0.66 1 1 1 1 1 2 1.265 0.59 0.8939391.065574 0.973981 0.927774 0.913516 3 2.46 0.56 0.848485 1.115880.907237 0.858978 0.831817 4 3.605 0.55 0.833333 1.150442 0.8172610.78351 0.753537 5 4.725 0.55 0.833333 1.171171 0.717801 0.7005570.676966 6 5.835 0.57 0.863636 1.160714 0.618698 0.620205 0.601079 76.965 0.59 0.893939 1.135371 0.524528 0.532371 0.523824 8 8.13 0.620.939394 1.087866 0.438568 0.448188 0.444177 9 9.35 0.64 0.9696971.027668 0.362027 0.360769 0.360769 10

TABLE II lists parameters for a series of alternating facets focused ontwo neighboring elements, such as an emitter and a neighboring receiver.In TABLE II, facets nos. 1-5 are focused on an emitter, and facets nos.6-9 are focused on a neighboring receiver. Three values are listed foreach facet; namely, its width, B, its location, x-pos, along the x-axisrelative to the center of the central facet for the emitter, and thelocation, border_pos, of the facet's outer edge. All facet values arespecified in millimeters.

TABLE II Nine alternating facets Facet no. B x-pos border pos 1 0.66 00.33 9 0.64 0.65 0.97 2 0.59 1.265 1.56 8 0.62 1.87 2.18 3 0.56 2.462.74 7 0.59 3.035 3.33 4 0.55 3.605 3.88 6 0.57 4.165 4.45 5 0.55 4.7255 5Signals Generated by Element 530

Reference is made to FIG. 65, which is a simplified illustration of atouch screen with a wide light beam crossing the screen, in accordancewith an embodiment of the present invention. Reference is also made toFIG. 66, which is a simplified illustration of a touch screen with twowide light beams crossing the screen, in accordance with an embodimentof the present invention. Reference is also made to FIG. 67, which is asimplified illustration of a touch screen with three wide light beamscrossing the screen, in accordance with an embodiment of the presentinvention. As shown in FIG. 65, a screen 800 is surrounded with emittersand receivers. A wide beam 167 is shown representing a wide detectionarea on screen 800, that is detected by an emitter-receiver pair200-300. Wide beam 167 is generated by optical elements, such as element530 described hereinabove but not shown in FIGS. 65-67. A first element530 collimates light from emitter 200, and a second element 530 focuseswide beam 167 onto receiver 300. A graph 910 shows the gradient ofsignal intensities detected across the width of wide beam 167.

FIG. 66 shows neighboring wide beams 168 and 169, representing widedetection areas on screen 800 detected by respective emitter-receiverpairs 201-301 and 202-302. Respective graphs 911 and 912 illustrate thegradient of signal intensities detected across the widths of wide beams168 and 169.

FIG. 67 shows the three wide beams of FIGS. 5 and 66. As seen in FIG.67, the left half of beam 167 is overlapped by half of beam 168, and theright half of beam 167 is overlapped by half of beam 169. The intensitygradients in graphs 910-912 indicate that a touch at any location alongthe width of beam 167 is detected along two gradients of two overlappingwide beams. Similarly, a touch at any location on the screen is detectedin both the vertical and the horizontal axis along two gradients of twooverlapping wide beams on each axis. A precise touch coordinate iscalculated by interpolating touch locations of the two signals based onthe detection signal gradients. FIG. 62 shows the light signalattenuation gradients 920 and 921 across the widths of the twooverlapping beams. Light signal attenuation gradient 920 corresponds tothe beam emitted from emitter element 200, and light signal attenuationgradient 921 corresponds to the beam emitted from emitter element 201.As such, the beam has maximum intensity directly above the element, andtapers off at either side. Having two different sloping gradients forthe overlapping beams is of advantage for calculating a precise touchlocation, as described hereinbelow.

Reference is made to FIG. 68, which is a simplified graph of lightdistribution of a wide beam in a touch screen, in accordance with anembodiment of the present invention. The lower portion of FIG. 68 showsa path across wide beam 167, and the upper portion of FIG. 68 is a graphdepicting signal intensity distribution along this path. The graph'sx-axis represents the horizontal screen dimension in units ofmillimeters. The graph's y-axis represents the baseline signal intensitydetected by emitter-receiver pair 200-300 situated at 10 mm along thescreen axis. The signal corresponds to a screen with emitter andreceiver elements arranged at a pitch of 10 mm. As such, the detectedwide beam spans 20 mm. The spikes in the graph are caused by thealternating facets of optical element 530 describe above, whichalternately focus rays at neighboring elements. As such, spikescorrespond to facets belonging to the measured emitter-receiver pair,and the neighboring troughs correspond to facets belonging to aneighboring emitter-receiver pair. Despite these spikes, detectionsignals of a finger or another object along the measured screen axishave a relatively smooth gradient along the entire 20 mm span of thebeam since the finger is wider than the narrow spike and troughchannels. As such, a finger blocks a series of spikes which remainsubstantially uniform as the finger slides long the screen axis. E.g., afingertip is approximately 6 mm wide, whereas there are 8-9 spikes in 10mm in the graph of FIG. 68.

Reference is made to FIG. 69, which is a simplified illustration ofdetection signals from three wide beams as a fingertip moves across ascreen, in accordance with an embodiment of the present invention. Shownin FIG. 69 are three detection signals of a fingertip as it moves acrossthree neighboring wide beams along a screen axis. From each of thesignals it is apparent that as the finger enters a wide beam, the fingerblocks a small portion of the beam. As the finger moves along the axistoward the center of the beam, it blocks progressively more of the beamuntil it blocks roughly 40% of the beam intensity, indicated in thegraph by a minimum detection of 60% of the expected baseline signal. Asthe finger moves further along, it blocks progressively less of thebeam. The shape of the detection curve is relatively smooth, despite thepeaks and troughs in the light beam shown in FIG. 68. There are slightfluctuations along the detection curves of FIG. 69 that are at leastpartially due to the peaks, but these fluctuations are minimal and donot significantly distort the trend of the signal.

Reference is made to FIGS. 70-72, which are simplified graphs of lightdistribution in overlapping wide beams in a touch screen, in accordancewith an embodiment of the present invention. Taken together, FIGS. 68and 70-72 show a light distribution across three neighboring wide lightbeams on a screen with emitter-receiver pairs spaced 10 mm apart. Asseen in these figures, the facets of optical element 530 provideoverlapping touch detection by two emitter-receiver pairs. FIG. 70 showsthe light signal from an emitter-receiver pair situated at location 0along the measured screen axis. FIG. 71 shows the light signal from anemitter-receiver pair situated at a location 20 mm along the measuredscreen axis. FIG. 72 shows the light signals from the threeemitter-receiver pairs of FIGS. 68, 70 and 71, and shows how these lightbeams cover overlapping areas of the screen surface. FIG. 69 shows threedetection signals for the three emitter-receiver pairs of FIG. 72, as afingertip moves along the screen axis.

Touch detection signals are less smooth when using a fine-point stylusthan when using a finger. E.g., a 2 mm stylus tip moving across a screengenerates more fluctuations in a detection signal than does a 6 mmfinger, since the stylus tip covers fewer peaks in the light signal and,therefore, moving in and out of a signal peak changes a larger part ofthe blocked signal. Nevertheless, embodiments of the present inventionovercome this drawback and determine stylus touch locations with a highlevel of accuracy, by interpolating multiple detection signals.

Reference is made to FIG. 73, which is a simplified graph of detectionsignals from a wide beam as a fingertip moves across a screen at threedifferent locations, in accordance with an embodiment of the presentinvention. Shown at the bottom of FIG. 73 are three paths 925-927 tracedby a finger across a wide beam 167. Path 925 is near LED 200, path 926is mid-screen, and path 927 is near a PD 300. The graph in the upperportion of FIG. 73 shows three detection signals of a fingertip as ittraverses the three paths 925-927, labeled in the graph legend as LEDedge, Midscreen and PD edge, respectively. The three detection signalsin the graph are substantially overlapping. As such, the signal isuniformly detected along its depth, and the signal varies as a functionof the touch along only one axis of the screen. Thus determining a touchlocation along a first axis is independent of the detection signal alonga second axis. Moreover, the intensity of the signal is uniform alongthe second axis, making the signal robust.

Supporting Various Screen Sizes

Some embodiments of configuration no. 6 include optical elements withalternating facets that are focused on two neighboring light emitting orreceiving elements. When such an optical element is separate from thelight emitters or receivers, the emitters or receivers are generallyspaced at a particular pitch. When such an optical element is formed asa rigid module together with an emitter or a receiver, the embeddedemitter or receiver is precisely positioned with respect to thereflective facets. The facets aimed at a neighboring module, are aimedin accordance with the embedded emitter or receiver in the neighboringmodule that is similarly situated in its module. Such positioningpotentially restricts the size of a screen to integral multiples of thepitch. E.g., with a pitch of 10 mm between emitters, the screendimensions must be integral multiples of 10 mm. Embodiments of thepresent invention are able to overcome this restriction, as described inwhat follows.

Reference is made to FIG. 74, which is a simplified diagram of fouroptical elements and four neighboring emitters, in accordance with anembodiment of the present invention. Shown in FIG. 74 are four opticalelements 531-534 arranged in a row. Each element is positioned oppositea respective one of emitters 200-203. The same configuration isassembled for receivers, or for alternating emitters and receivers. Inthe case of receivers, emitters 200-203 are replaced by receivers; andin the case of alternating emitters and receivers, emitters 200 and 202are replaced by receivers.

Optical elements 531, 532 and 534 are all of the same width, e.g., 10mm; i.e., w1=w2=w4. The pitch, P1, between emitters 200 and 201 is astandard distance, e.g., 10 mm. The facets of optical element 531 areconstructed for emitters that are at a standard pitch of 10 mm. PitchesP2 and P3 may be nonstandard. By enabling a device manufacturer toinsert a single emitter at a non-standard pitch, the manufacturer canaccommodate any screen size. The width, w3, of optical element 533 iscustomized for a non-standard screen size; e.g., for a screen length of96 mm, w3 is 6 mm instead of 10 mm, and pitches P2 and P3 are each 8 mm.Optical element 532 is a hybrid element—the left half of element 532 hasfacets aimed at emitters 200 and 201, which are positioned according toa standard 10 mm pitch, and the right half of element 532 is specialhaving facets aimed at emitters 201 and 202, where emitter 202 has anon-standard placement. Optical element 534 is also a hybrid element, asits left half has facets aimed at emitters 202 and 203, whereas itsright half is aimed at two standard pitch emitters. Optical element 533is non-standard throughout—it is not as wide as the standard elementsand has every other of its facets aimed at emitter 202. In this example,the width of the beam from emitter 202 is roughly 16 mm, as compared tothe standard 20 mm width. As such, emitter 202 is placed slightly closerto optical element 533.

Diffractive Surfaces

As described hereinabove, diffractive surfaces are used in embodimentsof the present invention to direct beams from two emitters along acommon path. Reference is made to FIG. 75, which is a simplified diagramof a diffractive surface that directs beams from two emitters along acommon path, in accordance with an embodiment of the present invention.Shown in FIG. 75 are emitters 200 and 201 emitting arcs of light 107 and108 into two collimating lenses 525. Wide beams 167 and 168 exit lenses525 and enter refractive surface 560, which directs both beams 167 and168 into a wide beam 193 that crosses the screen. A similar opticalarrangement splits wide beam 193 onto two receivers at the oppositescreen edge. Each emitter is activated separately with a respectiveopposite receiver. Beams from the two emitters have different signalgradients along the width of beam 193, as explained hereinabove. The twodetection signals are used to calculate a touch location from EQS. (2)and (3) provided hereinbelow.

Parallel Overlapping Beams

As described hereinabove, parallel wide beams projected at slightlydifferent heights over a screen are used in alternative embodiments ofthe present invention, to provide multiple detection signals for a touchevent on the screen.

Alternating Emitters and Receivers

In an alternative embodiment of the present invention, emitters andreceivers are positioned alternately along each screen edge. Referenceis made to FIG. 76, which is a simplified diagram of a touch screensurrounded with alternating emitters and receivers, in accordance withan embodiment of the present invention. Reference is also made to FIG.77, which is a simplified illustration of a touch screen surrounded withalternating emitters and receivers, and a wide beam crossing the screen,in accordance with an embodiment of the present invention. Reference isalso made to FIG. 78, which is a simplified illustration of a touchscreen surrounded with alternating emitters and receivers and two widebeams crossing the screen, in accordance with an embodiment of thepresent invention. Reference is also made to FIG. 79, which is asimplified illustration of a touch screen surrounded with alternatingemitters and receivers and three wide beams crossing the screen, inaccordance with an embodiment of the present invention. FIGS. 77-79 showoverlapping wide beams, similar to those of FIGS. 65-67 describedhereinabove.

Reference is made to FIG. 80, which is a simplified illustration of acollimating optical element reflecting and interleaving light for anemitter and a neighboring receiver, in accordance with an embodiment ofthe present invention. FIG. 80 shows optical element 530 interleavingneighboring light beams, wherein a first beam is outgoing from emitter200 and a second beam is incoming to neighboring receiver 301. FIG. 80also shows signal gradient 920 for the first beam and signal gradient921 for the second beam. When a touch is detected on both beams, thesloping gradients enable determination of a precise touch location byinterpolation, as described hereinbelow.

As indicated hereinabove with reference to FIG. 73, the detection signaldoes not vary with depth of touch location within a wide beam.Therefore, the opposing directions of the adjacent overlapping widebeams do not affect the touch detection signal. In turn, this enablesinterpolating signals from overlapping beams without regard fordirection of each beam.

As explained above with reference to configuration no. 4, when a touchpointer is expected to be wide, such as a finger, the wide beams neednot overlap, since it is expected that the finger span at least aportion of two neighboring beams, assuming the beams are slightly lesswide than the finger. Moreover, the finger covers each beam beginning atone of the beam's edges. Therefore, even when the beam distributes lightevenly across the beam's width, the system is able to determine theblocked portion of each beam. E.g., if 50% of the beam is blocked, thefinger is blocking half of the beam; and if 25% of the beam is blocked,the finger is blocking one quarter of the beam. This is different thanthe attenuated signal gradients 920 and 921 of FIG. 80. The location ofthe finger is then determined by interpolating signals from two or moreneighboring beams.

Multi-Touch Detection

Multi-touch locations are often difficult to identify unambiguously vialight emitters that emit light in directions parallel to two axes.Reference is made to FIGS. 81-84, which are illustrations of multi-touchlocations that are ambiguous vis-à-vis a first orientation of lightemitters, in accordance with an embodiment of the present invention. Asshown in FIGS. 81 and 82, there is ambiguity in determining thelocations of a diagonally oriented multi-touch. There is furtherambiguity if a multi-touch includes more than two pointers. For example,the two-touch cases shown in FIGS. 81 and 82 are also ambiguousvis-à-vis the three-touch case shown in FIG. 83 and vis-à-vis thefour-touch case shown in FIG. 84. In each of these cases, row and columnindicators a-h show an absence of light in the same locations. Suchambiguity is caused by “ghosting”, which refers to an effect where theshadow of one pointer obscures a portion of another pointer.

In accordance with an embodiment of the present invention, ghosting isresolved by use of two sets of grid orientations for touch detection.

Reference is made to FIGS. 85-87, which are illustrations of themulti-touch locations of FIGS. 81-83 that are unambiguous vis-à-vis asecond orientation of light emitters, in accordance with an embodimentof the present invention. Use of an arrangement of alternating emittersand receivers, as described hereinabove with reference to FIGS. 76 and77, and use of additional optical elements to generate two sets ofdetection axes, provide important advantages. One advantage isgenerating a robust set of overlapping wide beams, whereby multipledetection signals may be interpolated in order to determine touchcoordinates with high precision. Another advantage is generatingoverlapping wide beams on the second axis set, such that touch detectionon the second axis set is also precise.

A dual-unit light guide is described hereinabove with reference to FIGS.45 and 46. As described there, the lower portion 464 of the light guidecontains reflective facets or lenses that are focused on the emittersand receivers, and the upper portion 463 includes reflective surface andlenses that do not require precision placement vis-à-vis the emittersand receivers. In configuration no. 6, the alternating reflective orrefractive facets form part of the lower portion. A three-sidedrefractive cavity for distributing light beams in three directions isformed as part of the upper portion. In configuration no. 6, use ofmicro-lenses 467 is not required. Alternatively, the alternating facetsare formed in transparent plastic modules that include an emitter orreceiver, as described hereinbelow with reference to FIG. 112. Anarrangement of these modules replaces lower portion 464, and upperportion 463 remains.

Reference is made to FIG. 88, which is a simplified illustration of atouch screen with light beams directed along four axes, in accordancewith an embodiment of the present invention. Shown in FIG. 88 is a rowof light emitters 200 along the top edge of a screen 800, and a row oflight receivers 300 along the bottom edge of screen 800. The left andright edges of screen 800 include opposing rows of combinedemitter-receiver elements 230. Elements 230 act as emitters and asreceivers. In an embodiment of the present invention, an emitter and areceiver are combined in a single unit, such as the reflective andtransmissive sensor manufactured by Vishay Corporation of Malvern, Pa.In another embodiment of the present invention, an LED is used for bothlight emission and detection. An integrated circuit that both emits anddetects light using an LED and a current limiting resistor, is describedin Dietz, P. H., Yerazunis, W. S. and Leigh, D. L., “Very low costsensing and communication using bidirectional LEDs”, Internationalconference on Ubiquitous Computing (UbiComp), October, 2003.

Reference is made to FIG. 89, which is a simplified illustration of analternate configuration of light emitters and light receivers with twogrid orientations, in accordance with an embodiment of the presentinvention. Shown in FIG. 89 are light emitters 200 in an alternatingpattern with light receivers 300 around a screen perimeter. Lightemitted by each emitter is detected by two receivers at an oppositescreen edge, the two receivers being separate by an emittertherebetween.

In order that the light from an emitter arrive at the outer edges of twoopposite receivers, the wide beams emitted from each emitter must span adistance of three optical lenses. This is in contrast to theconfiguration described above with shift-aligned emitters and receivers,where the two receivers that detect light from a common emitter arepositioned adjacent one another, and thus the wide beams emitted fromeach emitter need only span a distance of two optical lenses.

Reference is made to FIG. 90, which is a simplified illustration of aconfiguration of alternating light emitters and light receivers, inaccordance with an embodiment of the present invention. As shown in FIG.90, emitter 201 is situated between receivers 303 and 304 along thebottom screen edge, and emitter 202 is situated between receivers 301and 302 along the top screen edge. Light from emitter 201 is detected byreceivers 301 and 302, and light from emitter 202 is detected byreceivers 303 and 304.

Reference is made to FIG. 91, which is a simplified illustration of twowide light beams from an emitter being detected by two receivers, inaccordance with an embodiment of the present invention. Shown in FIG. 91are two wide beams from emitter 201 that exit lens 440 and arrive atlenses 441 and 443 for detection by receivers 301 and 302, respectively.One wide beam is bordered by edges 145 and 146, and the other wide beamis bordered by edges 147 and 148. A cross-hatched triangular areaindicates an overlap where a touch is detected at receivers 301 and 302.

Reference is made to FIG. 92, which is a simplified illustration of twowide beams and an area of overlap between them, in accordance with anembodiment of the present invention. One wide beam, from emitter 201,exits lens 440 and arrives at lens 441 for detection by receiver 301.The wide beam is bordered by edges 145 and 146. Another wide beam, fromemitter 202 to receiver 303, is bordered by edges 147 and 148. Across-hatched diamond-shaped area indicates an overlap where a touch isdetected at receivers 301 and 303.

It will thus be appreciated by those skilled in the art that anylocation on the screen is detected by two emitter-detector pairs, whenthe emitter-detector pairs are situated at opposite screen edges and, assuch, an accurate touch location may be calculated as describedhereinabove.

Reference is made to FIG. 93, which is a simplified illustration of atouch point 980 situated at the edges of detecting light beams, inaccordance with an embodiment of the present invention. FIG. 93 showsthat it is desirable that the light beams extend to the edges of theemitter and receiver lenses, in order to accurately determine thelocation of touch point 980.

Reference is made to FIG. 94, which is a simplified illustration of afinger-sized touch point in a screen designed for finger touchdetection, in accordance with an embodiment of the present invention.FIG. 94 shows a large touch point 980, such as a finger touch, andalternating beams 201-301, 202-302 and 203-303. A detection signal isshown next to each detector in the form of a rectangle, indicating auniform light distribution along the width of the beam. Beams 201-301and 202-302 have portions blocked by pointer 980. The location ofpointer 980 is determined based on the blocked portions of beams 201-301and 202-302. In this case, the beams are neatly collimated and span onlyone lens, not three.

Reference is made to FIG. 95, which is a simplified illustration of anemitter along one edge of a display screen that directs light toreceivers along two edges of the display screen, in accordance with anembodiment of the present invention. Shown in FIG. 95 are a first pairof light beams emitted from an emitter 200 at one edge of a displayscreen to receivers 300 and 301 along the opposite edge of the displayscreen, and a second pair of light beams emitted from emitter 200 toreceivers 302 and 303 along the adjacent left edge of the displayscreen. A third pair of light beams (not shown) is emitted from emitter200 to receivers at the adjacent right edge of the display screen. Thesecond and third pairs of light beams are each oriented at an angle ofapproximately 45° relative to the first pair of light beams.

Also shown in FIG. 95 is a lens 439, used to refract light from emitter200 to lenses 442 and 443, which are oriented at approximately 45° tothe left of lens 439. In an embodiment of the present invention, lens439 is made of a plastic material, which has an index of refraction onthe order of 1.4-1.6. As such, an angle of incidence of approximately84° is required in order for the light to be refracted at an angle of45°. However, for such a large angle of incidence, the amount of lightlost due to internal reflection is large. In order to improvethroughput, two air/plastic interfaces are used to achieve an angle ofrefraction of approximately 45°, as described hereinabove.

Tri-Directional Micro-Lenses

Reference is made to FIGS. 96 and 97, which are simplified illustrationsof a lens for refracting light in three directions, having a lenssurface with a repetitive pattern of substantially planar two-sided andthree-sided recessed cavities, respectively, in accordance withembodiments of the present invention. The flat surface opposite theemitter or receiver is distal to the emitter or receiver in FIG. 96forming a three-sided cavity, and is proximal thereto in FIG. 97separating two two-sided cavities.

Such three-sided lenses are used in several embodiments. In a firstembodiment, the lens is used without an additional optical componentwith alternating facets for interleaving neighboring beams. In thisembodiment, wide beams cover the screen but do not necessarily overlapto provide two or more detection signals for interpolation. A typicaluse case for this embodiment is finger input, but not stylus input. Thetri-directional lens enables detection on four different axes, toeliminate ambiguity and ghosting in multi-touch cases. Thetri-directional lens also provides additional touch locationinformation; namely, four axes instead of two, and the additionalinformation increases the precision of the touch location, even for asingle touch.

In a second embodiment, the lens is used with an additional opticalcomponent with alternating facets for interleaving neighboring beams, orwith an alternative arrangement providing overlapping detection signals.In this embodiment, overlapping wide beams provide two or more detectionsignals for interpolation. Typical use cases for this embodiment arefinger and stylus input. The tri-directional lenses and the interleavingfacets may be formed in two distinct components. The interleaving facetscomponent is positioned closer to its emitter or receiver than thetri-directional component, since the tolerance for imprecise placementof the interleaving facets component is low, whereas the tolerance forimprecise placement of the tri-directional lens component is high.Alternatively, the tri-directional lenses and the interweaving facetsmay be formed in a single rigid component. For example, a diffractivegrating interleaves signals from two sources and also splits the beamsin three directions.

Shown in FIG. 96 is a lens 527 with a pattern of micro-lenses 528 on itsbottom surface. The micro-lens pattern shown in FIG. 96 has threesubstantially planar sides, each side refracting light in a differentdirection. The pattern of micro-lenses 528 form a saw-tooth repetitivepattern along the bottom edge of the upper section of the lens. Thethree walls of each micro-lens 528 are slightly curved, in order tospread the light in a wider arc as it exits the lens toward an intendedreceiver.

A collimating lens section (not shown) is situated beneath lens 527, todirect the light in parallel beams into micro-lenses 528.

In some embodiments of the present invention, lens 527 is part of atwo-lens arrangement, with lens 527 forming the upper of the two lenses,farther from the emitter or receiver, and nearer to the screen surface.In distinction, the two-section lens shown in FIG. 45 has a micro-lenspattern on the top of the lower section.

In order to properly interleave collimated beams from the alternatingfacets component, the pitch of the three-sided cavities needs to be muchsmaller than the pitch of the alternating facets. Ideally, the pitch ofthe cavities should be made as small as possible. With alternatingfacets of about 0.6 mm, the cavities should be 0.2 mm or smaller. Thedihedral angle between each pair of adjacent planes is approximately122°, to achieve a 45° refraction using plastic having a refractiveindex of 1.6. However, different angles may be desired for a differentset of diagonal axes, or plastic having a different refractive index maybe desired, in which case the dihedral angle will be different.

As shown in FIG. 96, incoming collimated light is refracted through twoair/plastic interfaces, to emerge at an angle of refraction that isapproximately 45°. The first interface, along an inner plane of themicro-lens, refracts the incoming light to an angle of refraction thatis approximately 58°, and the second interface refracts the light toemerge at an angle of refraction that is approximately 45°.

Reference is made to FIGS. 98-100, which are simplified illustrations ofa touch screen surrounded with alternating emitters and receivers anddiagonal wide beams crossing the screen, in accordance with anembodiment of the present invention. FIGS. 98 and 99 show diagonal widebeams from emitter 200 and 201 to receiver 300, and a correspondingsignal gradient 910. FIG. 100 shows diagonal wide beams from emitters202 and 204 to receivers 302 and 304, and corresponding signal gradients911 and 912. These wide beams overlap wide beam 167 of FIG. 95, therebyproviding multiple touch detections for interpolation.

Reference is made to FIG. 101, which is a simplified graph of lightdistribution across a diagonal wide beam in a touch screen, inaccordance with an embodiment of the present invention. The lowerportion of FIG. 101 shows a wide beam 167 and a path 925 crossing thisbeam according to a second axis system. If the pitch between elements is1 unit, then the width of this beam is 1/√2 units. Thus if the pitchbetween elements is 10 mm, then the beams along the diagonal axes areapproximately 7 mm across. The upper portion of FIG. 101 shows thedistribution of light across wide beam 167. The signal spans acrossapproximately 14 mm of the diagonal beam, as compared with 20 mm of thevertical beam in FIG. 69. As described above with reference to FIG. 68,the signal gradient across the width of the beam enables interpolatingmultiple detection signals to determine a precise touch position.

Reference is made to FIG. 102, which is a simplified graph of lightdistribution across three overlapping diagonal wide beams in a touchscreen, in accordance with an embodiment of the present invention. FIG.102 shows a signal distribution across three overlapping beams in asecond axis system, similar to FIG. 72. Different widths are covered bythese two sets of beams.

Reference is made to FIG. 103, which is a simplified graph of touchdetection as a finger glides across three overlapping diagonal widebeams in a touch screen, in accordance with an embodiment of the presentinvention. FIG. 103 shows how reception of a finger passing across threeadjacent overlapping beams is detected by each beam. The maximumdetection signal is approximately 40% of the baseline signal intensity,and this occurs when the finger is in the middle of the beam. In thiscase, the finger blocks approximately 60% of the total light of thebeam. This is greater than the amount of light blocked by the samefinger in FIG. 69; namely, 40%. The difference is due to the diagonalbeam being narrower than the vertical beam. Therefore a 6 mm fingertipblocks a greater portion of light in the beam. The detection signals aresubstantially smooth and robust for determining touch locations.

Reference is made to FIG. 104, which is a simplified graph of detectionsignals from a diagonal wide beam as a fingertip moves across the screenat three different locations, in accordance with an embodiment of thepresent invention. FIG. 104 shows that touch detection remains stablealong depth of a wide beam, and varies only according to its locationacross the width of the beam, as described hereinabove with reference toFIG. 73.

Reference is made to FIG. 105, which is a simplified illustration of afirst embodiment for a touch screen surrounded with alternating emittersand receivers, whereby diagonal and orthogonal wide beams crossing thescreen are detected by one receiver, in accordance with an embodiment ofthe present invention. FIG. 105 shows an embodiment with an equal numberof elements positioned along each screen edge. Three beams 167-169 areshown for one receiver 300; namely, one directed to an opposite emitter200 and the other two directed to emitters 201 and 202 on adjacentscreen edges. The diagonal beams generate two axes that are notperpendicular to one another.

Reference is made to FIG. 106, which is a simplified illustration of asecond embodiment for a touch screen surrounded with alternatingemitters and reciters, whereby diagonal and orthogonal wide beamscrossing the screen are detected by one receiver, in accordance with anembodiment of the present invention. FIG. 106 shows an embodiment withdifferent numbers of elements positioned along adjacent screen edges.Three beams 167-169 are shown for one receiver 300; namely, one directedto an opposite emitter 200, and the other two directed at substantially45° angles to emitters 201 and 202, one of which is on an opposite edgeand another of which is positioned on an adjacent edge. These diagonalbeams generate two axes that are perpendicular to one another.

Palm Rejection

When a user rests his hypothenar muscles, located on the side of hispalm beneath his little finger, on a touch screen when writing with astylus, ghosting generally occurs. This part of the palm blocks a largearea of the touch screen, and often blocks a series of light beams alongthe screen's vertical axis, thereby hiding the stylus' touch positionalong the vertical axis.

Reference is made to FIG. 107, which is a simplified illustration of auser writing on a prior art touch screen with a stylus. Shown in FIG.107 is a hand 930 holding a stylus 931, and drawing a line 932 on atouch screen 800. The user's palm is resting on screen 800, blocking twoseries of light beams depicted as dotted lines; namely, a series 113along the screen's horizontal axis, and a series 114 along the screen'svertical axis. The location of the stylus tip on the vertical axis iswithin series 114. Beam 115 does detect the tip of the stylus, but itonly provides a horizontal axis location.

Embodiments of the present invention overcome the drawback illustratedin FIG. 107. Reference is made to FIG. 108, which is a simplifiedillustration of light beams detecting location of a stylus when a user'spalm rests on a touch screen, in accordance with an embodiment of thepresent invention. By providing two sets of detection axes; namely, anorthogonal set and a diagonal set, a two-dimensional location of astylus is determined. FIG. 108 shows that beams 115 and 116 uniquelydetect a stylus. Since each detection comprises overlapping wide beamswhose signals are interpolated, as described hereinabove, the stylusposition is determined with high precision, despite beams 115 and 116not being perpendicular to one another. When the bottom of the user'spalm does not block diagonal beam 117, then beam 117 also detects thestylus location separately from the palm. In such case, beams 116 and117 are used to detect the stylus location. Alternatively, all threedetecting beams 115-117 may be used.

Another challenge that arises with touch screens that support bothstylus and finger input arises when a user places his palm on the screenin order to write with a stylus, is misinterpretation of the initialcontact between palm and screen as being a tap on an icon, in responseto which the device launches an unintended application whose icon wastapped. Once the palm is resting on the screen, an area of contact isused to reject the palm touch as a screen tap. Nevertheless, the initialcontact may cover a small surface area of the screen and thus bemisinterpreted as a screen tap.

According to embodiments of the present invention, light beams above thescreen are used to detect a palm as it approaches the screen. In oneembodiment this is accomplished by projecting light from each emitter atseveral heights above the screen, as illustrated in FIG. 18 showing anapproaching finger 900 blocking beam 101 but not beam 102. In anotherembodiment, multiple layers of emitters and receivers are arrangedaround the screen, and used to detect objects at different heights abovethe screen, as described hereinabove with reference to a user inputgesture cavity and, in particular, with the cavity frame folded on topof the screen.

Reference is made to FIG. 109, which is a simplified illustration of aframe surrounding a touch screen, in accordance with an embodiment ofthe present invention. FIG. 109 shows a frame 849 surrounding a touchscreen, similar to frame 849 of FIG. 55. Two stacked rows of emitters200 and receivers 300 are provided in the frame. When assembled togetherwith a display in an electronic device, the stacked rows of emitters andreceivers are raised above the display surface and provide objectdetection at two heights, namely, on the screen by the lower row ofemitters and receivers, and above the screen by the upper row ofemitters and receivers. When a user's palm begins to touch the screen, alarge palm area is detected hovering above the screen. This enables thedevice to determine that a palm is approaching the screen, and that anyscreen tap is inadvertent.

In another embodiment of the present invention, only one row of emittersand receivers is provided for detecting a palm hovering above thescreen, and touches on the screen are detected by conventional detectionsystems imposed on the display including inter alia capacitive orresistive touch sensors.

According to an embodiment of the present invention, a user interfacedisables screen taps for activating functions when a palm is detected.When the palm is detected, the user interface is configured to launchapplications in response to a user touching an icon and gliding hisfinger away from the touched location along the touch screen. I.e., twosets of user interface gestures are provided. When no palm is detected,the first set of gestures is used. With the first set of gestures, a tapon an icon activates an application or function associated with theicon. When a palm is detected hovering above the screen, the second setof gestures is used. With the second set of gestures, the user isrequired to touch an icon and then glide his finger away from the touchlocation along the touch screen in order to activate the application orfunction associated with the icon. In this way, the device does notlaunch an unintended application when a user places his palm on thescreen. The second set of gestures does not disable activation of icons;it enables the user to activate the application or function associatedwith the icon, if he desires to do so, by a touch and glide gesture.

Situating Elements around Corners

Screen corners present several challenges for arranging emitters andreceivers. One challenge is that two emitters need to be placed in thesame location—one for each screen edge. The challenge is complicated bythe layout illustrated in FIG. 44, whereby the emitter and receiverelements are positioned under the screen surface, and therefore therectangle formed by these elements is smaller than the frame of lensessurrounding the screen. One approach to overcoming this challenge isplacement of two emitters at approximately the same location on the PCB,with one of the emitters placed on the top surface of the PCB and theother emitter placed on the bottom surface of the PCB. However, thisapproach introduces complications with connectors and positioning ofoptical elements.

Another challenge is extending overlapping beams to the edges of thescreen. Although the emitters and receivers are underneath the screen,touch detection covers the entire area bordered by the inner edges ofthe optical elements that surround the screen.

Embodiments of the present invention provide arrangements that aresuitable for use with orthogonal and diagonal detection axes, asdescribed hereinabove. Reference is made to FIG. 110, which is asimplified illustration of a first embodiment of emitters, receivers andoptical elements for a corner of a touch screen, in accordance with anembodiment of the present invention. FIG. 110 shows a first cornerarrangement of emitter or receiver elements and their respective opticalelements. Receivers 300-303 and emitters 200-202 are arrangedalternatingly along two adjacent screen edges. Solid lines indicatelight beams from the emitters, and dashed lines indicate light beamsarriving at the receivers. Emitters and receivers 300, 200, 302, 202 and303 are positioned according to a standard pitch, and optical elements530 are configured accordingly. Receiver 301 and emitter 201 areoriented at an angle, and their wide beams are divided such that half ofa beam traverses the screen in a first direction, e.g., along thescreen's vertical axis, and the other half of the beam traverse thescreen in a second direction, e.g., along the screen's horizontal axis.Moreover, in embodiments that include a second lens having three-sidedcavities for splitting beams, as described hereinabove, half of the widebeam is split into a first pair of diagonal beams that originate alongone screen edge, and the other half of the beam is split into a secondpair of diagonal beams that originate along an adjacent screen edge. Ahybrid optical element 531 is provided in order to overlap beams foremitter 201 and receiver 302. Optical element 531 is referred to as a“hybrid optical element” because the right half of the element is thesame as the right half of element 530, but a portion of the reflectiveor refractive facets on the left half are directed at the non-standardlocation and orientation of emitter 201. Similarly, a hybrid opticalelement 532 is provided in order to overlap beams for emitter 200 andreceiver 301. The lower half of hybrid optical element 532 is similar tothe left half of element 530. Both halves of corner element 533 areuniquely configured; namely, the left half overlaps beams for emitter201 and receiver 301, and the right half overlaps beams for emitter 201and receiver 302. Both halves of corner optical element 534 are alsouniquely configured for emitters 200 and 201 and for receiver 301.

Reference is made to FIG. 111, which is a simplified illustration of asecond embodiment of emitters, receivers and optical elements for acorner of a touch screen, in accordance with an embodiment of thepresent invention. FIG. 111 shows an alternative corner arrangement ofemitter or receiver elements and their respective optical elements. Inthe arrangement shown in FIG. 111, only one emitter 201 is placed at anon-standard pitch and orientation. Standard optical elements 530 areused together with hybrid optical elements 531 and 532 and unique corneroptical elements 533. Optical elements 531-533 are configured for theemitter-receiver arrangement shown, and are therefore different thanelements 531-533 of FIG. 110.

Integrated Modules

In general, there is low tolerance for assembly errors for touch systemsusing alternating reflective or refractive facets aimed at two foci. Anoffset in placement of an emitter or a receiver causes it to be out ofthe reflective facet's focus, which can degrade accuracy and performanceof such systems. In accordance with an embodiment of the presentinvention, rigid modular blocks containing reflective or refractivefacets and an emitter or a receiver are prepared, in order to ensure therequired assembly precision. Such modular blocks are useful forsimplifying the process of integrating touch screen components, and forminimizing the tolerance chain for a manufacturer. These modular blocksare formed so as to be easily positioned together in a row along an edgeof a display, for fast assembly of a touch screen. The high tolerancerequirements of placing an emitter or receiver in exactly the correctposition vis-à-vis the reflective or refractive facets, are handledduring manufacture of the modular blocks, thus removing the burden ofhigh precision assembly from a device manufacturer.

Simplified manufacturing is achieved by integrating optical elements andelectronic components into a single unit. As such, complex surfaces maybe gathered into one component, thereby reducing the need for highassembly tolerances.

Reference is made to FIG. 112, which is an illustration of opticalcomponents made of plastic material that is transparent to infraredlight, in accordance with an embodiment of the present invention. Shownin FIG. 112 is an optical component 488 that includes a forward-facingLED 236, and electronics to handle the LED signal. Optical component 488is connected to electrical pads 760 and 761. Optical component 488 isused to transmit collimated light beams from two emitters; namely,emitter 235 and emitter 236. Emitter 235 is included in a neighboringoptical component 489. In the alternating emitter-receiver embodimentdescribed hereinabove, optical component 488 is used to transmitcollimate light beams for one emitter and one receiver. E.g.,neighboring module 489 includes a receiver instead of emitter 235.

Light beams from emitter 235 exit optical component 489 through atight-fitting surface 491, and enter optical component 488 through atight-fitting surface 490. FIG. 105 shows non-parallel light beams fromemitters 235 and 236 hitting alternating facets on a wave-likemulti-faceted reflective surface 493. Components 488 and 489 aresubstantially identical, and fit together. A device manufacturer canthus use these components as building blocks to create a touch screen,by arranging a series of these building blocks in a row along each edgeof the display. Typical arrangements are (a) two adjacent display edgesare lined with emitter components, and the other two edges are linedwith receiver components, and (b) all four display edges are lined withalternating emitter/receiver components, i.e., each emitter has aneighboring receiver. Indeed, the emitter and receiver components, beingof substantially identical shape, can be positioned together in the samerow.

An optical component 494 is similar to optical component 488, exceptthat an LED 237 is side-facing instead of forward-facing. FIG. 112 showscollimated light beams 100 exiting optical component 494. Pins 989 and990 guide optical component 494 on a printed circuit board.

Optical component 495 is optical component 488 as viewed from the front.FIG. 112 shows collimated light beams 100 exiting optical component 495.

Similar optical components (not shown) are also provided for receivinglight beams that traverse the screen surface. For these components, theemitters are replaced by receivers, and the electrical components handlethe receiver signals. Such optical components receive collimated lightbeams, and direct the beams onto two different receivers.

Reference is made to FIG. 113, which is a simplified diagram of a sideview of a touch screen with light guides, in accordance with anembodiment of the present invention. Shown in FIG. 113 are a display642, an optical element 496, a photo diode 394 within optical element496, an optical element 497, and an emitter 238 within optical element497. Optical elements 496 and 497 are connected to a printed circuitboard 762. Emitter 238 emits non-parallel light beams and, as describedhereinabove with reference to FIG. 112, the non-parallel beams areconverted into collimated beams, or substantially collimated beams,before exiting optical element 497. Another portion of the non-parallelbeams are collimated by a neighboring module, not shown in FIG. 112. Thebeams 100 that exit optical element 497 are directed upwards and arereflected over display 642 by a light guide 498. In an embodiment of thepresent invention, three-way refracting cavities are etched, orotherwise formed, on the lower surface of optical element 498 to refractthe light beams in three directions in order to provide two coordinatesystems for determining a touch location. The light beams 100 enter alight guide 499 on the opposite side of screen 642, and are reflectedbelow display 642 into optical element 496. In embodiments supportingthe two coordinate systems, the three-way refracting cavities arepresent on the underside of optical element 499 as well. As describedhereinabove, optical element 496 and its neighboring optical element,not shown, focus the incoming light beams on photo diode 394. In oneembodiment of the present invention, the light guides 498 and 499 areconstructed as a frame that surrounds display 642.

In the touch screen of FIG. 113, two types of light beam redirectionoccur. A first redirection requires multiple facets directed at a singlefocus point. A second redirection uniformly redirects incoming beams ata 90° angle, or folds incoming light beams into a narrow waist or focus,as described hereinabove with reference to configuration no. 5. In someembodiments, the collimated beams are refracted in three directions, inbetween the first and second redirections, by refracting cavities.

The first type of redirection requires that the emitter or receiver bepositioned at a specific location relative to the focal point of manyfacets. As such, the positioning of the emitter or receiver and itsreflective surfaces, is sensitive to variations in placement. Thus theassembly of the emitter or receiver, together with its correspondingsurface of reflective facets, has a low tolerance of error. The secondtype of redirection, involving reflection and, in some cases, uniformrefraction in three directions, is robust to variations in position ofthe reflector and to the pattern of refracting cavities located in thelight guide. Thus assembly of this portion of the light guide has a hightolerance for error.

The light guides that reflect light above the screen surface may bemanufactured separately and assembled with other touch screencomponents. Thus in FIG. 113 light guides 498 and 499 are shown separatefrom optical elements 496 and 497.

Reference is made to FIG. 114, which is an illustration of a touchscreen with a block of three optical components on each side, inaccordance with an embodiment of the present invention. Blocks 500 and501 are emitters, and blocks 502 and 503 are receivers. The blockscreate an active area 991, where an x-y touch position of a stylus orfinger may be calculated based on detected blocked light. Adding moreoptical components of the same type to each block serves to enlarge theactive area that is created.

Reference is made to FIG. 115, which is a magnified illustration of oneof the emitter blocks of FIG. 114, in accordance with an embodiment ofthe present invention. Shown in FIG. 115 are three emitters 239, 240 and241, that emit respective wide beams 167, 168 and 169 from one edge of ascreen, which are read as respective signals 170, 171 and 172. Thesignal gradients are indicated by their diagonal orientations. At theopposite edge of the screen, signals 170, 171 and 172 are eachredirected onto respective receivers by respective optical components.An accurate position of an object, such as a finger or stylus, touchingthe screen, is then determined based on values of blocked light at thereceivers, as described below.

Touch Screen System Configuration No. 7

Configuration no. 7 uses total internal reflection in a touch screen.Whereas in configurations 1-6 the light beams travel in air above thescreen surface, in configuration no. 7 the light beams travel through asheet of glass or plastic that is transmissive to the wavelengths usedin the touch detection system. In other embodiments, the light travelsthrough a liquid or gel layer that is transmissive to the wavelengthsused in the touch detection system.

Total internal reflection is an optical phenomenon that occurs when aray of light strikes a medium boundary at an angle larger than aparticular critical angle, with respect to the normal to the surface. Ifthe refractive index is lower on the other side of the boundary and theincident angle is greater than the critical angle, no light passesthrough the boundary and all of the light is reflected. The criticalangle is the angle of incidence above which the total internalreflection occurs.

When a light beam crosses a boundary between materials with differentrefractive indices, the light beam is partially refracted at theboundary surface, and partially reflected. However, if the angle ofincidence is greater (i.e., the ray is closer to being parallel to theboundary) than the critical angle—the angle of incidence at which lightis refracted such that it travels along the boundary—then the lightstops crossing the boundary altogether and instead is totally reflectedback internally. This only occurs where light travels from a medium witha higher refractive index to one with a lower refractive index. Forexample, it occurs when passing from glass to air.

A touch screen according to configuration no. 7 has a glass or plasticsheet or pane above the display screen referred to as a cover glass.Alternatively, a gel layer or a liquid filled sac is placed over thedisplay. The cover glass, or gel or liquid filled sac material istransparent to light at the wavelength used. Typically optical touchsystems use wavelengths in the near infrared range, i.e., wavelengthsbelow 1100 nm, e.g., 940 nm. A narrow air gap is provided between thecover glass and the display such that both the upper and lower surfacesof the cover glass, exposed to air, internally reflect light inside thecover glass. Using any of the collimating lenses described above withreference to configurations 1-6, light enters the cover glass from belowat an angle larger than the critical angle with respect to the normal tothe cover glass surface, and is directed through the cover glass bytotal internal reflection. A finger touching the cover glass from aboveabsorbs a portion of the light inside the cover glass at the touchedlocation. In addition, the finger also scatters a portion of the lightinside the cover glass at the touched location. Both of these actionsdiminish the amount of light that arrives at a respective detector, andthe detector measurement is used as described herein to calculate thelocation of the touch.

Reference is made to FIG. 116, which is a simplified illustration of atouch screen assembly having a cover glass, in accordance with anembodiment of the present invention. FIG. 116 shows a screen 635, acover glass 646, emitters 200, emitter lenses 564, receivers 300 andreceiver lenses 565. FIG. 116 shows a view from above, and a crosssection along the line A-A. The emitters and receivers in FIG. 116 areshift-aligned, and the lenses ensure that light from each emitterreaches two opposite receivers.

Reference is made to FIG. 117, which is a simplified illustration of atouch object scattering internally reflected light in a screen assemblyhaving a cover glass, in accordance with an embodiment of the presentinvention. FIG. 117 shows scattering of light by an object touching thescreen. Light beams 120 from emitter 201 to receivers 301 and 302 areinternally reflected inside cover glass 646 and scattered by a touchobject 900. FIG. 117 shows scattered beams 121. However, a portion ofthe detection channel beams 122 beneath touch object 900 arrive atreceivers 301 and 302.

Reference is made to FIG. 118, which is a simplified illustration of atouch object absorbing internally reflected light in a screen assemblyhaving a cover glass, in accordance with an embodiment of the presentinvention. FIG. 118 shows absorption of light by a finger 900 touchingthe screen. The light beams from emitter 201 to receiver 301 areinternally reflected inside cover glass 646 and are partially absorbedinto finger 900.

Reference is made to FIG. 119, which is a simplified illustration of atouch screen assembly having a cover glass, in accordance with anembodiment of the present invention. FIG. 119 shows the lens arrangementof FIGS. 60 and 61 modified for a system according to configuration no.7. As in FIG. 60, an LED 200 is coupled with a pair of lenses 550 and551, separated by an air gap 555, for collimating light. In addition,FIG. 119 includes cover glass 646 that receives light beams emitted byemitter 200 and transmits the beams through cover glass 646 using totalinternal reflection. This lens differs from that of FIG. 60 in that itis entirely below the height of the device. Also, lens 551 includes anadditional reflective facet 562 for guiding light into the underside ofcover glass 646 at a suitable angle α, i.e., at an angle less than thecritical angle with respect to the cover glass surface, as illustratedin FIG. 120. For example, the critical angle for a glass-to-air boundaryis roughly 46° so a suitable angle α in this case is 40°. The actualrefractive indices of the cover glass material, air, and a low-indexadhesive, if such is used to laminate the cover glass to the display,determine the critical angle for each embodiment. Lens 551 is connectedto cover glass 646 using an optically clear transfer tape 561, e.g.,TESA 69304 optically clear pure acrylic adhesive manufactured by TESACorp. of Charlotte, N.C., so that this reflected light enters coverglass 646. A similar arrangement at an opposite edge of the screenguides the light out of cover glass 646 and onto one or more respectivephoto detectors. In other embodiments light guide 551 is formed as aunitary molded plastic unit together with cover glass 646 and adhesivetransfer tape 561 is not used. In an alternative embodiment light enterscover glass 646 from the side instead of from underneath, as illustratedin FIG. 121.

Reference is made to FIG. 120, which is a simplified illustration of alight beam path in the touch screen assembly of FIG. 119, in accordancewith an embodiment of the present invention. Reference is also made toFIG. 121, which is a simplified illustration of a touch screen assemblyhaving a cover glass, in accordance with an embodiment of the presentinvention. FIG. 120 shows the path of light beam 151 from emitter 200through lenses 550 and 551 and into cover glass 646 at a suitable angleα where it propagates by virtue of total internal reflection. FIG. 121shows air gap 563 between cover glass 646 and display 635. This air gapcreates the necessary medium boundary on the underside of the coverglass for total internal reflection inside cover glass 646.Alternatively, the necessary medium boundary for total internalreflection is provided by laminating the cover glass to the screen usinga suitable low-index adhesive. Cover glass 646 is preferably 1-2 mmthick.

Configuration 7 differs from configurations 1-6 in the amount of lightblocked during a touch. In general, a touch in configuration nos. 1-6blocks more of the beam than a comparable touch in configuration no. 7.However principles such as gradations of intensity along the width ofthe beams described hereinabove, inter alia with reference to FIGS. 47,48 and 68-76, are the same in configuration no. 7 as they are inconfiguration nos. 1-6. Therefore the methods for interpolating signalsdescribed herein are applicable to configuration no. 7, once the loweramount of light beam blockage in configuration no. 7 is accounted for.The arrangement of divergent beams where three divergent wide beams aredirected out of each emitter, as described in detail with reference toFIGS. 79-83, 91-92 and 99-109, is also applicable to configuration no. 7with the divergent beams all being directed into the cover glass at anappropriate angle for total internal reflection.

Configuration no. 7 enables designing a device without a protrudingbezel around the screen. This is an advantage over configurations 1-6 interms of design.

Another advantage relates to multi-touch detection. In configurations1-6, when two or more objects are inserted into a light beam pathsimultaneously, the light beam shadow patterns no longer correspond tounique finger positions, and therefore the signal pattern is ambiguous.Examples of different touch patterns that produce the same shadow signalare shown in FIGS. 85-87. In systems using total internal reflection,each touch results in a further partial reduction in the signal so thatthe number of touches between transmitter and receiver may becalculated.

This calculation is simplest if the system assumes that only one type ofitem may be placed on the screen. Otherwise, a thick finger could bemistaken for two thin fingers, for example. However, in many cases thereis a delay between each of the touches in a multi-touch gesture. Whenthe system detects incremental steps in the magnitude of the touchdetection signal, it indicates that the signal is generated by multipletouches as opposed to a large touch object. Thus when the system samplesthe screen at a high frequency, such that new samples are generated aseach additional touch is added, the system determines that an additionaltouch occurred due to the further partial reduction in the signal. Inparticular, when using the controller described below, the system cansample the screen at rates of up to 1000 Hz, enabling discriminatingbetween touches that occur at almost the same time.

Another advantage provided by configuration no. 7 relates to scatteringof light by the touch object. A finger touching the screen scatters aportion of the light inside the cover glass at the touched location. Thelenses 550 and 551 collimate the light from the emitter 200 and directit at one or more respective detectors. The scattering of light by atouch object results in the light reaching other detectors. Thecollimating lenses associated with the detectors direct light scatteredfrom a point along the collimated path onto the detectors. Therefore, incases that may indicate multi-touch, the system polls additionaldetectors and resolves the multi-touch locations based on the detectionof scattered light.

An example illustrates this advantage, with reference to FIG. 122, whichis a simplified illustration of emitters and receivers detecting twodiagonal touch points, in accordance with an embodiment of the presentinvention. FIG. 122 shows an arrangement of emitters 200 and PDreceivers 300 surrounding a touch screen according to configuration no.7. Two touch points 971 and 972 are drawn. Emitters 200 and PD receivers300 are both numbered 1-16. A reduction in expected light occurs at PDnumbers 2, 7, 11 and 15 and, as already explained, this signal patternis not unique to these two touch points. In this case the systemactivates emitter number 2 and samples two PDs: PD number 11 and PDnumber 15. Each detector has an associated collimating lens not shown inthe figure. In the touch pattern drawn, PD number 15 will detect agreater amount of scattered light (by touch point 971) than PD number 11because touch point 971 is situated along the path of the collimatinglens associated with PD number 15 but not along the path of thecollimating lens associated with PD number 11. Similarly, the systemactivates emitter number 15 and samples two PDs: PD number 2 and PDnumber 7. In the touch pattern drawn, PD number 2 will detect a greateramount of scattered light (by touch point 971) than PD number 7. Basedon this, the system determines that the touches are at the locationsshown and not at the opposite corners of the screen.

Reference is made to FIG. 123, which is a simplified illustration ofemitters and receivers detecting three touch points, in accordance withan embodiment of the present invention. Continuing the example of FIG.122, FIG. 123 adds a third touch point 980. In this case, PD number 7detects a significantly greater reduction in expected light from itsrespective emitter (number 7) than PD number 2 detects from itsrespective emitter (number 2). This is because two touches (972, 980)absorb light from emitter 7, but only one touch (971) absorbs light fromemitter 2. Based on this, the system determines that the touches are atthe locations shown.

Reference is made to FIG. 124, which is a simplified illustration of atouch screen assembly having a cover glass, in accordance with anembodiment of the present invention. With respect to scattered light, inthe touch screen of FIG. 124, during activation of emitter 15, detectors7 and 2 detect scattered light from touch points 971 and 980respectively; whereas during activation of emitter 2, detector 15detects scattered light from touch point 971, and detector 11 detectsmuch less scattered light. This indicates that touch point 980 is at thebottom right of the screen and not at the upper left corner.

In general, an activation sequence of emitters and detectors aimed atdetecting scattered light may be employed selectively. For example, itmay be performed only when a potential ghosted gesture is possible.Also, the sequence aimed at detecting scattered light may be limited toactivating only those emitter-detector pairs that are likely to resolvethe ghosting; e.g., when the detection pattern of FIGS. 122 and 123occurs, only activating emitter-detector pairs 15-2, 15-7, 2-11 and2-15.

Reference is made to FIG. 125, which is a flowchart of a method fordisambiguating multiple touch detection signals in accordance with anembodiment of the present invention. At step 1060 emitter-receiver pairsaround a touch screen are scanned. A reduction in expected lightindicates a touch along the emitter-receiver signal paths. If at leasttwo x-coordinate channels and at least two y-coordinate channels detecta touch, the system proceeds through steps 1063-1065 to correctly pairthe x, y coordinates. At step 1063 the system pairs each x coordinateemitter with all of the detected y-coordinate receivers to create asecond set of touch detection channels. In these channels, a touch isindicated by an increase in detected light that results from light beingscattered by the touch object. At step 1064 the system pairs eachy-coordinate emitter with all of the detected x-coordinate receivers tocreate a similar set of touch detection channels. At step 1065 thesystem determines the most likely touch, based on steps 1063 and 1064,and outputs the touch coordinates at step 1062.

If only one x-coordinate or only one y-coordinate is returned at step1061 the system outputs touch coordinates at step 1062 as follows: ifone x-coordinate and one y-coordinate are detected, then output one x,ytouch coordinate. If multiple coordinates are detected along one axis,pair each of these one axis coordinates with the single x ory-coordinate on the other axis.

Touch Screen System Configuration No. 8

Configuration no. 8 combines over-air light beams, as in configurations1-6, with total internal reflection light beams as described inconfiguration 7. In certain embodiments, each emitter-detector pairactivation includes a first portion of light traveling in air above thescreen, and a second portion of light traveling through a cover glass.Both portions of light originate at the emitter and arrive at thedetector.

Reference is made to FIG. 126, which is a simplified illustration of atouch screen assembly having a cover glass, in accordance with anembodiment of the present invention. FIG. 126 shows two light beams 151and 152 in a touch system according to configuration no. 8. Both beamsoriginate at emitter 200 and both beams converge onto an oppositedetector not shown in the figure. Beam 151 is directed into cover glass646 from beneath, and beam 152 is directed over air, above cover glass646. Light guide 498 guides both beams from emitter 200.

Configuration no. 8 has several advantages. This configuration detects ahovering object that blocks a portion of the over-air beam. However, ahovering object does not affect the total internal reflection; actualcontact with the cover glass is required to frustrate the total internalreflection. As such, there is a significant drop in the signal whencontact occurs. This enables the system to clearly distinguish a hovergesture from a touch gesture.

Another advantage is that configuration no. 8 has two detection systems:the over-air beams and the total internal reflection beams. When one ofthese systems is impaired, the other system provides touch detection.For example, a narrow stylus point is accurately traced by the over-airbeams as described hereinabove, but the narrow stylus point does notabsorb or frustrate much of the total internal reflection beams.

Yet another advantage is that the total internal reflection system isavailable to resolve ghosted gestures, as explained above with referenceto configuration no. 7.

Touch Screen System Configuration No. 9

Configuration no. 9 uses a reduced number of components by coupling anemitter or a receiver to one end of a long thin light guide situatedalong an edge of the screen. Such a light guide is described in U.S.Pat. No. 7,333,095 entitled ILLUMINATION FOR OPTICAL TOUCH PANEL.

Reference is made to FIG. 127, which is an illustration of a touchscreen having a long thin light guide 514 along a first edge of thescreen, for directing light over the screen, and having an array oflight receivers 300 arranged along an opposite edge of the screen fordetecting the directed light, and for communicating detected lightvalues to a calculating unit 770, in accordance with an embodiment ofthe present invention. Light emitters 200 are coupled to both ends oflight guide 514. Light guide 514 is positioned along one edge of a touchscreen 800. Light is emitted into light guide 514 along a screen edge,and is re-directed across the screen surface by a reflector 515. Aplurality of receivers 300 is situated along the opposite edge of touchscreen 800, to enable multiple receivers to detect a touch, as describedhereinabove with reference to configuration nos. 2 and 3.

Reference is made to FIG. 128, which is an illustration of a touchscreen having an array of light emitters 200 along a first edge of thescreen for directing light beams over the screen, and having a long thinlight guide 514 for receiving the directed light beams and for furtherdirecting them to light receivers 300 situated at both ends of lightguide 514, in accordance with an embodiment of the present invention.Detected light values at receiver 300 are communicated to a calculatingunit (not shown). According to another embodiment of the presentinvention, only one light receiver 300 is coupled to one end of lightguide 514. Light guide 514 is positioned along one edge of a touchscreen 800. A plurality of emitters is situated along the opposite edgeof the touch screen, to enable receiver(s) 300 to detect a touch basedon serial activation of multiple emitters, as described hereinabove withreference to configuration nos. 2 and 3. Light emitted across the screensurface is re-directed by a reflector 515. Light is received into lightguide 514 along the screen edge and is directed through the length oflight guide 514 onto a receiver 300.

Reference is made to FIG. 129, which is an illustration of two lightemitters, 201 and 202, each emitter coupled to an end of a long thinlight guide 514, in accordance with an embodiment of the presentinvention. Light guide 514 is positioned along one edge of a touchscreen. Light 100 is emitted into light guide 514 along a screen edge,and is re-directed across the screen surface by a reflector 515. Aplurality of receivers is situated along the opposite edge of the touchscreen, to enable multiple receivers to detect a touch, as describedhereinabove with reference to configuration nos. 2 and 3. Each emitter201 and 202 is activated separately, and the receivers thus detect atouch based on blocked light from each of the two emitters. The amountof light 100 emitted at any given location along the length of the lightguide decreases as a function of the distance between the location andthe emitter. As such, different amounts of detected light from eachemitter 201 and 202 are used to calculate the precise location of atouch, as described hereinabove with reference to configuration nos. 2and 3.

Embodiments of the present invention improve upon the light guide ofU.S. Pat. No. 7,333,095, by etching or otherwise forming micro patterns516 on the outer surface of the light guide, in order to widely refractoutgoing light beams 101 of FIG. 127, or incoming light beams 102 ofFIG. 106, as described hereinabove with reference to configuration nos.2 and 3. Micro patterns 516 are a uniform substantially parallel patternof grooves along light guide 514, and are simpler to form than the fanpattern described hereinabove with reference to configuration no. 2.Light guide 514 also includes a light scatterer strip 517 inside oflight guide 514. Micro patterns 516 and light scatterer strip 517 appearin FIGS. 127 and 128.

Touch Screen System Configuration No. 10

Configuration no. 10 enables detecting pressure on a touch screen, asapplied during a touch operation. Detecting pressure enablesdiscrimination between a light touch and a hard press, and is useful foruser interfaces that associate separate actions to a touch and a press.E.g., a user may select a button or icon by touching it, and activatethe function associated with the button or icon by pressing on it. Sucha user interface is described in applicants' co-pending U.S. applicationSer. No. 12/486,033, entitled USER INTERFACE FOR MOBILE COMPUTER UNIT.

In some embodiments of the present invention, a touch enabled deviceincludes a base plane, such as a PCB, a light guide frame rigidlymounted on the base plane, and a resilient member attached to the baseplane to suspend or “float” a non-rigidly mounted touch screen insidethe light guide frame. A press on the touch screen deflects the floatingtouch screen along a z-axis, exposing more of the light guide frame. Alight guide frame reflector, which directs light over the screen asdescribed hereinabove, is formed so that the exposure allows more lightto traverse the screen. In this way, when a hard press on the screenoccurs, many of the receivers detect a sudden increase in detectedlight. Moreover, detection of a hard press may be conditioned upon atouch being detected at the same time, thus preventing false detectionof a hard press due to a sudden increase in ambient light. When thedownward pressure is released, the resilient member returns the screento its original position within the light guide frame.

Reference is made to FIGS. 130-133, which are illustrations of a touchscreen 800 that detects occurrence of a hard press, in accordance withan embodiment of the present invention. FIG. 130 shows touch screen 800in rest position, screen 800 being supported by resilient supportingmembers 841 and 842 that create a flex air gap 843, which are mounted ona printed circuit board 700. FIG. 130 shows two light guides, 518 and519, one on either side of screen 800, for directing light 100 from anemitter 200 over screen 800 to a receiver 300. Only a small upperportion of each light guide 518 and 519 extends above screen 800.Receiver 300 communicates detected light intensities to a calculatingunit (not shown).

FIG. 133 shows a finger 900 pressing down on the screen, causing members841 and 842 to compress and to narrow flex air gap 843. As a result, alarger portion of light guides 518 and 519 are exposed above screen 800,thus allowing (a) more light 100 from emitter 200 to traverse screen 800and be detected by receiver 300, and (b) more ambient light 101 to reachreceiver 300. In various embodiments, either or both of these increasesin detected light are used to indicate a hard press. In otherembodiments, the amount of downward pressure applied is determined basedon the amount of additional detected light, thus enabling discriminationbetween more hard and less hard touches.

In some embodiments, the light guide frame includes protruding lips 520and 521, shown in FIG. 132, that extend over the edges of screen 800, tocounter balance the upward force of resilient members 841 and 842 whenno downward pressure is applied to screen 800. Resilient members 841 and842 may comprise inter alia a flexible mounting material, a torsionspring, an elastic polymer body, or a hydraulic suspension system. FIG.133 shows emitters 200, receivers 300 coupled with calculating unit 770,and resilient members 841 and 842 arranged on a single PCB 700.

In other embodiments, the touch screen is not displaceable relative tothe frame. However, the screen flexes or bends somewhat in response to ahard press. The bending of the screen causes a sudden increase indetected light in many of the receivers, indicating a hard press on thescreen. As indicated hereinabove, detection of a hard press may beconditioned upon a touch also being detected at the same time, thuspreventing false detection of a hard press in response to trauma to thedevice.

Reference is made to FIGS. 134 and 135, which are bar charts showingincrease in light detected, when pressure is applied to a rigidlymounted 7-inch LCD screen, in accordance with an embodiment of thepresent invention. The bar charts show the amount of light detected fromeach emitter along one edge of the screen when a soft touch occurs (FIG.134), and when a hard touch occurs (FIG. 135). The light emitters andlight receivers are shift-aligned, so that light from each emitter isdetected by two receivers. As such, two bars are shown for each emitter,indicating the light detected by each of the two receivers. Both barsindicate that a touch is detected at receivers opposite LED 4, where nolight is detected. The bar charts show that more light is detected fromneighboring emitters in the case of a hard touch, than in the case of asoft touch.

Operation of Configurations Nos. 2 and 3

The following discussion relates to methods of operation forarrangements of the optical elements shown in configurations nos. 2 and3, around a touch screen, used in conjunction with the cover glassdescribed above with reference to configurations nos. 6 and 7, toachieve accurate touch detection based on total internal reflection.These methods are of advantage for pen and stylus support, which havefine touch points, and provide highly accurate touch locationdetermination for single-finger and multi-finger touches as well.

Reference is made to FIGS. 136 and 137, which are illustrations ofopposing rows of emitter lenses and receiver lenses in a touch screensystem, in accordance with an embodiment of the present invention.Positioned behind each emitter and receiver lens is a correspondingrespective light emitter 200 or light receiver 300. As shown in FIG.138, each emitter 200 is positioned opposite two receivers 300 thatdetect light beams emitted by the emitter. Similarly, each receiver 300is positioned opposite two emitters 200, and receives light beamsemitted from both emitters.

FIG. 136 shows (A) a single, full beam 173 from an emitter 200 thatspans two receivers 300; (B) the portion of the full beam, designated174, detected by the left one of the two receivers 300; (C) the portionof the full beam, designated 175, detected by the right one of the tworeceivers 300; (D) multiple beams 176, for multiple emitters 200,covering the touch screen, and (E) multiple beams 177, for multipleemitters 200, covering the touch screen. Generally, each emitter 200 isactivated alone. Precision touch detection is described hereinbelow,wherein a touch point is detected by multiple beams. It will beappreciated from (D) and (E) that points on the screen are detected byat least one beam 176 and one beam 177.

To conserve power, when the touch screen is idle only one set of beams,namely, beams 176 or beams 177, are scanned in a scanning sweep, andonly for the axis with the smallest number of emitters 200. The scanningtoggles between beams 176 and beams 177, and thus two scanning sweepsalong the axis activate every emitter-receiver pair along the axis. Theother axis, with the larger number of emitters, is only scanned wheneither a touch is present, or when a signal differs from its referencevalue by more than an expected noise level, or when an update ofreference values for either axis is being performed. Reference valuesare described in detail hereinbelow.

FIG. 137 shows (A) an emitter 201 sending light to a receiver 301 at anangle of 15° to the left; (B) emitter 201 sending light to a receiver302 at an angle of 15° to the right; (C) emitter 202 sending light toreceiver 302 at an angle of 15° to the left; and (D) a microstructurerefracting incoming light. The emitter lenses and receiver lenses shownin FIG. 137 are equipped with the microstructure shown in (D), in order(i) to emit light in both left and right directions from multiplelocations along the emitter lens surface, and (ii) to ensure that lightreceived at any angle of incidence at any location along the receiverlens surface is detected by the receiver.

Reference is made to FIG. 138, which is a simplified illustration of atechnique for detecting a touch location, by a plurality ofemitter-receiver pairs in a touch screen system, in accordance with anembodiment of the present invention. Shown in FIG. 138 is an opticalemitter lens 506 of width k, positioned opposite two optical receiverlenses 508 and 509, each of width k, on a touch screen. A pointer, 900,touching the screen blocks a portion of the light beam emitted fromoptical emitter lens 506. Optical emitter lens 506 emits overlappingbeams that cover both optical receiver lenses 508 and 509. The spreadangle of the wide beam depends on the screen dimensions, and on the lenswidth, k, along the x-axis. Another optical emitter lens 507 is alsoshown, shifted by half an element width, m, below an optical receiverlens 510.

In accordance with an embodiment of the present invention, at least onesurface of optical emitter lens 506 is textured with a plurality ofridges. Each ridge spreads a beam of light that spans the two opposingreceiver lenses 508 and 509. As such, light from each of many pointsalong the surface of optical emitter lens 506 reaches both opposingreceiver lenses 508 and 509, and the light beams detected by adjacentreceivers overlap. In configuration no. 2 these ridges form a featherpattern, and in configuration no. 3 these ridges form a tubular pattern.

In accordance with an embodiment of the present invention, the ridgesform micro-lenses, each having a pitch of roughly 0.2-0.5 mm, dependingon the touch screen configuration. In the case of a feather pattern, theridges form a fan, and their pitch narrows as the ridges progress inwardand become closer together. In the case of a tubular pattern, the pitchof each micro-lens remains constant along the length of the micro-lens.

At least one surface of each receiver lens 508 and 509 is similarlytextured, in order that at least a portion of light arriving at each ofmany points along the receiver lens surface, arrive at the receiverphoto diode.

In accordance with an embodiment of the present invention, the output xand y coordinates are filtered temporally and spatially. The followingdiscussion relates to determination of the x-coordinate, and it will beappreciated by those skilled in the art that the same method applies todetermination of the y-coordinate.

Configurations nos. 2 and 3 show that a touch location is detected by atleast two emitter-receiver pairs. FIG. 138 shows two suchemitter-receiver pairs, 506-508 and 506-509, detecting a touch locationof object 900 along the x-axis. In FIG. 138, beams 506-508 are denotedby beam 178, and beams 506-509 are denoted by beam 179. FIG. 138 showsthree detection areas; namely, (i) the screen area detected byemitter-receiver pair 506-508, drawn as a wedge filled withright-sloping lines, (ii) the screen area detected by emitter-receiver506-509, drawn as a wedge with left-sloping lines, and (iii) the screenarea detected by both emitter-receiver pairs 506-508 and 506-509, drawnas a wedge with a crosshatch pattern. The left and right borders of thisthird screen area are shown as lines X₁ and X₂, respectively.

In order to determine the x-coordinate X_(p) of object 900's touchlocation (X_(p), Y_(r)), an initial y-coordinate, Y_(initial), isdetermined corresponding to the location along the y-axis of theemitter-receiver pair having the maximum touch detection signal amongall emitter-receiver pairs along the y-axis. In FIG. 138, thisemitter-receive pair is 507-510. The lines designated X₁ and X₂ in FIG.138 are then traversed until they intersect the line y=Y_(initial) atlocations (X_(a), Y_(initial)) and (X_(b), Y_(initial)). CoordinatesX_(a) and X_(b) are shown in FIG. 138. The x-coordinate of object 900 isthen determined using the weighted averageX _(p)=(W _(a) X _(a) +W _(b) X _(b))/(W _(a) +W _(b))  (2)where the weights W_(a) and W_(b) are normalized signal differences forbeam 178 and beam 179, respectively. The signal difference used is thedifference between a baseline, or expected, light value and the actualdetected light value. Such difference indicates that an object istouching the screen, blocking a portion of the expected light. Theweights W_(a) and W_(b) are normalized because the detection signal of atouch occurring near the row of emitters is different from a touchoccurring near the row of receivers, as described hereinbelow withreference to FIGS. 144-151. A touch screen design is tested to determinedifferent signal strength and attenuation patterns as an object crossesa beam at various portions along the length of the beam. Differentscenarios are tested, e.g., a scenario for objects near the beam'semitter, a scenario for objects near the beam's receiver, and a scenariofor objects in the middle of the screen. When a touch is detected, thedetection pattern of detecting receivers is analyzed to select anappropriate scenario, and the signals are normalized according to theselected scenario. Calibration and further normalization of the weightsis described hereinbelow. A similar weighted average is used todetermine the y-coordinate Y_(p).

If the pointer 900 is detected by more than two emitter-receiver pairs,then the above weighted average is generalized toX _(p)=Σ(W _(n) X _(n))/(ΣW _(n)),  (3)where the weights W_(n) are normalized signal differences, and the X_(n)are weight positions.

In one embodiment of the present invention, where the pointer 900 is asmall object, the largest signal difference is used in conjunction withthe two closest signals to calculate the position. This compensates forthe fact that the signal differences for small objects are small, andnoise thus becomes a dominant error factor. Use of the two closestsignals reduces error due to noise. In another embodiment of the presentinvention, only the two largest signal differences are used.

Reference is made to FIG. 139, which is an illustration of a light guideframe for the configuration of FIGS. 136 and 137, in accordance with anembodiment of the present invention. Shown in FIG. 139 are four edges ofa light guide frame, with optical emitter lenses 511 and opticalreceiver lenses 512. It is noted that the inner edges of the frame arenot completely covered by beams 182. As such, in some embodiments of thepresent invention only an inner touch area 993, indicated by the dashedrectangle, is used.

To reduce error due to signal noise, the final coordinate is determinedas the output of a temporal filter, using the spatially filtered currentcoordinate value, determined as above, and a previous coordinate value.The higher the filter weight given to the current x-coordinate, thecloser the output will be to that value, and the less will be the impactof the filter. Generally, use of substantially equal weights for bothcoordinate values results in a strong filter. In one embodiment of thepresent invention, the temporal filter is a low-pass filter, but otherfilters are also contemplated by the present invention. In accordancewith an embodiment of the present invention, different pre-designatedfilter weight coefficients may be used in different cases. In analternative embodiment, the filter weight coefficients are calculated asneeded.

Choice of appropriate filter coefficients is based on scanningfrequency, the speed at which a touch object is moving across thescreen, whether the object motion is along a straight line or not, andthe size of the touch object.

Generally, the higher the scanning frequency, the nearer the currentcoordinate value is to the previous coordinate value, and a strongerfilter is used. Scanning frequency is used to estimate the speed anddirection of movement of an object. Based on the scanning frequency, athreshold distance is assigned to two input values, the thresholdindicating fast movement. If the difference between the current andprevious coordinate values is greater than the threshold distance, aweaker filter is used so that the output coordinate not lag considerablybehind the actual touch location. It has been found by experiment thatthe filteroutput_val= 1/10*previous_val+ 9/10*current_val  (4)provides good results in this case. In addition, the lag value,described hereinbelow, is reset to equal the output value in this case.

If the difference between the current and previous coordinate values isless than the threshold distance, then a lag value is determined. Thelag value indicates speed and direction along an axis. In has been foundby experiment that the valuelag=⅚*lag+⅙*current_val  (5)provides good results in this case. The filter weight coefficients areselected based on the difference between the lag value and the currentcoordinate value. Generally, the greater this difference, whichindicates either fast motion or sudden change in direction, the weakerthe filter.

For example, if the touch object is stationary, the lag value eventuallyis approximately equal to the current coordinate value. In such case,signal noise may cause small differences in the spatially calculatedtouch position, which in turn may cause a disturbing jitter effect;i.e., the touch screen would show the object jittering. Use of a strongtemporal filter substantially dampens such jittering.

If the touch object is moving fast or makes a sudden change indirection, a strong temporal filter may create a perceptible lag betweenthe actual touch location and the displayed touch location. In the caseof a person writing with a stylus, the written line may lag behind thestylus. In such cases, use of a weak temporal filter reduces suchlagging.

When the touch object covers a relatively large screen area, such as afinger or other blunt object touching the screen, the lag between theactual finger motion and the displayed trace of the motion is lessperceptible, because the finger covers the area of the lag. In suchcase, a different temporal filter is used.

The type of object, finger vs. stylus, being used may be inferred byknowing expected user behavior; e.g., a user interface intended forfinger touch assumes a finger being used. The type of object may also beinferred by the shadowed area created by the object. The size of thetouch area as determined based on shadowed emitter signals, is thereforealso a factor used in selecting temporal filter weight coefficients.

Reference is made to FIG. 140, which is a simplified flowchart of amethod for touch detection for a light-based touch screen, in accordancewith an embodiment of the present invention. At operation 1021, acurrent coordinate value is received, based on a spatial filter thatprocesses signals from multiple emitter-receiver pairs. A thresholddistance is provided, based on a scan frequency. At operation 1022, thedifference between the current coordinate value and a previouscoordinate value is compared to the threshold distance. If thedifference is less than or equal to the threshold distance, then atoperation 1023 a new lag value is calculated, as in EQ. (5). Atoperation 1024 temporal filter weight coefficients are determined basedon the difference between the current coordinate value and the lagvalue. At operation 1025, the temporal filter is applied to calculate anoutput coordinate value, as in EQ. (4).

If, at operation 1022, the difference between the current coordinatevalue and previous coordinate value is greater than the thresholddistance, then weak filter weight coefficients are selected at operation1026. At operation 1027, the temporal filter is applied to calculate anoutput coordinate value, as in EQ. (4). At operation 1028 the lag valueis set to the output coordinate value.

Embodiments of the present invention provide a method and apparatus fordetecting a multi-touch operation whereby two touches occursimultaneously at two corners of a touch screen. An example of such amulti-touch is a rotation gesture, shown in FIGS. 141-143, whereby auser places two fingers 900 on a screen 800 and turns them around anaxis. As pointed out hereinabove with reference to FIGS. 15 and 16, itis difficult for a light-based system to discriminate between a top-left& bottom-right touch vs. a bottom-left & top-right touch. Use ofshift-aligned emitters and receivers enables such discrimination, asdescribed hereinbelow.

In accordance with an embodiment of the present invention, data fromreceivers along a first axis is used to determine a touch location alongtwo axes. Reference is made to FIGS. 144-147 which are illustrations ofa finger 900 touch event at various locations on a touch screen, andcorresponding FIGS. 148-151, which are respective bar charts of lightsaturation during the touch events, in accordance with an embodiment ofthe present invention. FIG. 144 shows a touch located near a row ofemitters, between two emitters. FIG. 145 shows a touch located near arow of receivers, blocking a receiver. FIG. 146 shows a touch locatednear a row of emitters, blocking an emitter. FIG. 147 shows a touchlocated near a row of receivers, between two receivers.

FIGS. 148-151 each include two bar charts; namely, an upper chartshowing light saturation at receivers along an x-axis, and a lower chartshowing light saturation at receivers along a y-axis. Each row ofreceivers is shift-aligned with an opposite row of emitters. As such,each emitter is detected by two receivers. Correspondingly, FIGS.148-151 show two bars for each emitter, one bar per receiver.

FIGS. 148-151 exhibit four distinct detection patterns. FIG. 148 showsan absence of light detected primarily by one receiver from its tworespective emitters. The absence of light is moderate. FIG. 149 shows anabsence of light detected primarily by one receiver from its tworespective emitters. The absence of light is large. FIG. 150 shows twoadjacent receivers detecting a large absence of expected light from theblocked emitter. Both receivers detect some light from neighboringelements. FIG. 151 shows two adjacent receivers detecting a moderateabsence of expected light from the blocked emitter. Both receiversdetect some light from neighboring emitters. TABLE III summarizes thesedifferent patterns.

TABLE III Patterns of touch detection based on proximity to andalignment with emitters and receivers No. of Receivers Amount of PatternNo. Detecting the Expected Light FIGS. Touch Location Touch that isBlocked 1 Near a row of 1 Moderate FIG. 142 emitters, between FIG. 145two emitters 2 Near a row of 1 Large FIG. 143 receivers, blocking FIG.147 a receiver 3 Near a row of 2 Large FIG. 144 emitters, blocking FIG.148 an emitter 4 Near a row of 2 Moderate FIG. 145 receivers, betweenFIG. 149 two receivers

According to an embodiment of the present invention, determination oflocation of a multi-touch is based on the patterns indicated in TABLEIII. Thus, referring back to FIG. 142, four detection points are shownalong two rows of receivers. Detections D1-D4 detect touch points 971 inupper-right & lower-left corners of the screen. Based on whether thedetection pattern of each point is of type 1 or 3, or of type 2 or 4,the detection patterns determine whether the corresponding touch iscloser to the emitters, or closer to the receivers. Each touch has twoindependent indicators; namely, the X-axis detectors, and the Y-axisdetectors. Thus, for detection points 971 in FIG. 142, detections D1 andD3 are of types 2 or 4, and detections D2 and D4 are of types 1 or 3. Indistinction, for detection points 971 in FIG. 142, detections D2 and D4are of types 2 or 4, and detections D1 and D3 are of types 1 or 3.

In addition to evaluation of detection points independently, the variousdetection patterns may be ranked, to determine which touch point iscloser to the emitters or to the receivers.

Moreover, when a rotate gesture is performed, from touch points 971 totouch points 972, movement of detections discriminates whether thegesture glides away from the emitters and toward the receivers, or viceversa. In particular, subsequent detections are compared, anddiscrimination is based on whether each detection pattern is becomingmore like type 1 or 3, or more like type 2 or 4.

Reference is made to FIG. 152, which is a simplified flowchart of amethod for determining the locations of simultaneous, diagonally opposedtouches, in accordance with an embodiment of the present invention. Atoperation 1031, two x-coordinates and two y-coordinates are detected,such as x-coordinates D1 and D2, and y-coordinates D3 and D4, shown inFIGS. 142 and 143. At operation 1032 the detected x-coordinates areanalyzed to identify a pattern of detection from among those listed inTABLE I. At operation 1033 the detected x-coordinates are rankedaccording to touches that occurred closer to or farther from adesignated screen edge, based on the pattern detected at operation 1032and based on the “Touch Location” column of TABLE III. The y-coordinatesrepresent distances from the designated edge. At operation 1034, eachranked x-coordinate is paired with a corresponding y-coordinate.Operations 1035-1037 are performed for the y-coordinates, similar tooperations 1032-1034 performed for the x-coordinates. At operation 1038,the two sets of results are compared.

Reference is made to FIG. 153, which is a simplified flowchart of amethod for discriminating between clockwise and counter-clockwisegestures, in accordance with an embodiment of the present invention. Atoperation 1041, two glide gestures are detected along an x-axis. Eachglide gesture is detected as a series of connected touch locations.Thus, with reference to FIGS. 142 and 143, a first glide gesture isdetected as a connected series of touch locations beginning atx-coordinate D1, and a second concurrent glide gesture is detected as aconnected series of touch locations beginning at x-coordinate D2. Atoperation 1042, the x-glide detections are analyzed to determine thetypes of detections that occurred in each series, from among thepatterns listed in TABLE III.

At operation 1043, the x-glide detections are ranked according totouches that occurred closer to or farther from a designated screenedge, based on the patterns of detections determined at operation 1042,and based on the “Touch Location” column of TABLE III. Operation 1043relates to series of connected touch detections over a time interval.Each series generally includes touch detections of patterns 1 and 3, orof patterns 2 and 4, listed in TABLE III, depending on whether the glidewas closer to or further away from the designated edge. In addition toanalyzing the individual detections that comprise a glide, the series oftouch detections is also analyzed to determine if the glide is movingcloser to or farther from the designated edge, based on comparison ofintensities of detections over time. E.g., in one series of detectionshaving multiple pattern 1 detections, if the amount of blocked lightincreases over time, then it is inferred that the glide is moving towardthe receivers, otherwise the glide is moving toward the emitters.

The y-coordinates represent distances from a designated edge, such asthe edge of emitters. At operation 1044 each ranked x-axis glide ispaired with a corresponding y-axis glide. Operations 1045-1047 areperformed for the y-axis glide, similar to operations 1042-1044performed for the x-axis glide. At operation 1048 the two sets ofresults are compared. At step 1049 a discrimination is made as towhether the rotation gesture is clockwise or counter-clockwise.

FIGS. 63 and 79 show alignments of emitters and receivers whereby rightand left halves of each beam overlap neighboring beams, as shown inFIGS. 70 and 82. Three beams are shown in these figures; namely, beams167, 168 and 169. The left half of beam 167 overlaps the right half ofbeam 168, and the right half of beam 167 overlaps the left half of beam169. As such, a touch at any location within beam 167 is detected by twobeams. The two detecting beams have different detection gradients alongthe widths of the beams, as shown by light detection areas 910-912 inthe figures.

The gradient of light attenuation is substantially linear across thewidth of the beam. As such, a weighted average of the differentdetection signals is used to calculate a position along one axis usingEQS. (2) and (3) above. EQ. (2) extends to a number, n, of samples.E.g., if a finger at the center of beam a blocks 40% of the expectedsignal of beam a, and blocks none of the expected signal of beam b, thenW_(a) and W_(b) are 0.4 and 0, respectively, and the location X_(p) iscalculated asX _(p)=(0.4*X _(a)0*X _(b))/(0.4+0)=X _(a).The same value of X_(p) is obtained for a stylus at the screen positionwhich, due to its being narrower than the finger, blocks only 20% of theexpected signal of beam a.

Similarly, if a finger between the centers of beams a and b blockssimilar amounts of expected light from both beams, say 30%, then X_(p)is calculated asX _(p)=(0.3*X _(a)+0.3*X _(b))/(0.3+0.3)=½(X _(a) +X _(b)),which is the midpoint between X_(a) and X_(b).

Location calculation in a system of aligned emitters and receiversdiffers in several aspects from location calculation in a system ofshift-aligned emitters and receivers. In a system of aligned emittersand receivers, beams are aligned with the coordinate system used forspecifying the touch location. In this case, the touch location iscalculated along a first axis without regard for the touch locationalong the second axis. By contrast, in a shift-aligned system theprimary beam coordinate, e.g., X_(a) for beam a, is determined based onan assumed touch coordinate on the second axis, Y_(initial).

Further, in a system of aligned emitters and receivers the attenuationand signal strength pattern generated by an object crossing the beam issubstantially the same at all locations along the length of the beam. Asdescribed hereinabove with reference to FIGS. 76 and 107, as an objectmoves across the width of a beam, it generates substantially similarsignal patterns whether it crosses the beam near the beam's emitter,detector or in mid-screen. Therefore, an initial normalizing of weights,W_(a), W_(b), . . . , W_(n), based on the detection pattern is requiredin shift-aligned systems, and is not required in aligned systems.

When a light-blocking object is placed at the center of a beam, such asbeam 167 in FIGS. 70 and 82, a portion of the neighboring beam isblocked. E.g., 40% of beam 167 is blocked and 5% of beam 168 is blocked.However, the signals include both random noise and also noise caused bythe alternating facets that may account for signal fluctuations. Atechnique is required to determine whether the touch is in fact at thecenter of beam 167, or slightly offset from the center.

In accordance with an embodiment of the present invention, multiplesamples of each signal are taken, and combined to filter out signalnoise. Additionally, the neighboring beams 168 and 169 are configured bytheir respective optical elements to overlap around the center of beam167, as seen in FIGS. 72 and 106 where all three signals detect touchesaround the center of the middle signal. In cases where the maindetection signal is concentrated in one beam, detection signals fromboth left and right neighboring beams are used to fine tune the touchlocation calculation. Specifically, filtered signals of neighboringbeams 168 and 169 are used to determine an offset from the center ofbeam 167.

In embodiments with optical elements with three-way lenses that createlight beams along two sets of axes, similar calculations are performedon the diagonal detection beams to determine locations on the secondaxis system. As described hereinabove, touch objects typically block alarger portion of the diagonal signals that of the orthogonal signals.

The spatial and temporal filters described hereinabove with reference toshift-aligned emitter-receiver arrangements are applied in alignedemitter-receiver arrangements as well.

Calibration of Touch Screen Components

Reference is made to FIG. 154, which is a simplified flowchart of amethod of calibration and touch detection for a light-based touchscreen, in accordance with an embodiment of the present invention. Ingeneral, each emitter/receiver pair signal differs significantly fromsignals of other pairs, due to mechanical and component tolerances.Calibration of individual emitters and receivers is performed to ensurethat all signal levels are within a pre-designated range that has anacceptable signal-to-noise ratio.

In accordance with an embodiment of the present invention, calibrationis performed by individually setting (i) pulse durations, and (ii) pulsestrengths, namely, emitter currents. For reasons of power consumption, alarge current and a short pulse duration is preferred. When a signal isbelow the pre-designated range, pulse duration and/or pulse strength isincreased. When a signal is above the pre-designated range, pulseduration and/or pulse strength is decreased.

As shown in FIG. 154, calibration (operation 1051) is performed at bootup (operation 1050), and is performed when a signal is detected outsidethe pre-designated range (operation 1055). Calibration is only performedwhen no touch is detected (operation 1053), and when all signals on thesame axis are stable (operation 1054); i.e., signal differences arewithin a noise level over a time duration.

Reference signal values for each emitter/receiver pair are used as abasis of comparison to recognize a touch, and to compute a weightedaverage of touch coordinates over a neighborhood. The reference signalvalue for an emitter/receiver pair is a normal signal level. Referencesignal values are collected at boot up, and updated when a change, suchas a change in ambient light or a mechanical change, is detected. Ingeneral, as shown in FIG. 154, reference signal values are updated(operation 1056) when signals are stable (operation 1054); i.e., whensignal variations are within an expected range for some number, N, ofsamples over time.

A touch inside the touch area of a screen may slightly bend the screensurface, causing reflections that influence detected signal values atphoto diodes outside of the touch area. Such bending is more pronouncedwhen the touch object is fine or pointed, such as a stylus. In order toaccount for such bending, when a touch is detected (operation 1053), allstable signals (operation 1058) outside the touch area undergo areference update (operation 1059). When no touch is present and allsignals are stable (operation 1054), but a signal along an axis differsfrom the reference value by more than the expected noise level(operation 1055), the emitters are calibrated (operation 1051).Recalibration and updating of reference values require stable signals inorder to avoid influence of temporary signal values, such as signalvalues due to mechanical stress by bending or twisting of the screenframe.

To further avoid error due to noise, if the result of anemitter/receiver pair differs from a previous result by more than anexpected noise level, a new measurement is performed, and both resultsare compared to the previous result, to get a best match. If the finalvalue is within the expected noise level, a counter is incremented.Otherwise, the counter is cleared. The counter is subsequently used todetermine if a signal is stable or unstable, when updating referencevalues and when recalibrating.

After each complete scan, signals are normalized with their respectivereference values. If the normalized signals are not below a touchthreshold, then a check is made if a recalibration or an update ofreference values is necessary. If a normalized signal is below the touchthreshold, then a touch is detected (operation 1053).

To reduce risk of a false alarm touch detection, due to a suddendisturbance, the threshold for detecting an initial point of contactwith the screen, such as when a finger first touches the screen, isstricter than the threshold for detecting movement of a point ofcontact, such as gliding of a finger along the screen while touching thescreen. I.e., a higher signal difference is required to detect aninitial touch, vis-à-vis the difference required to detect movement ofan object along the screen surface. Furthermore, an initial contact isprocessed as pending until a rescan verifies that the touch is valid andthat the location of the touch remains at approximately the sameposition.

To determine the size of a touch object (operation 1057), the range ofblocked signals and their amplitudes are measured. For large objects,there is a wait for detecting an initial point of contact with thescreen, until the touch has settled, since the touch of a large objectis generally detected when the object is near the screen before it hasactually touched the screen. Additionally, when a large objectapproaches the screen in a direction not perpendicular to the toucharea, the subsequent location moves slightly from a first contactlocation.

However, objects with small contact areas, such as a pen or a stylus,are typically placed directly at the intended screen location. As such,in some embodiments of the present invention, the wait for detecting aninitial contact of a fine object is shortened or skipped entirely.

It has been found advantageous to limit the size of objects thatgenerate a touch, in order to prevent detection of a constant touch whena device with a touch screen is stored in a pouch or in a pocket.

At operation 1053, it is also necessary to distinguish between signalsrepresenting a valid touch, and signals arising from mechanical effects.In this regard, reference is made to FIG. 155, which is a pictureshowing the difference between signals generated by a touch, and signalsgenerated by a mechanical effect, in accordance with an embodiment ofthe present invention. Each of the four graphs in FIG. 155 showsdetection beams 1-10 during a scan along one screen axis. As seen inFIG. 155, signal gradients discriminate between a valid touch and amechanical effect.

Reference is made to FIG. 156, which is a simplified diagram of acontrol circuit for setting pulse strength when calibrating alight-based touch screen, in accordance with an embodiment of thepresent invention. Reference is also made to FIG. 157, which is a plotof calibration pulses for pulse strengths ranging from a minimum currentto a maximum current, for calibrating a light-based touch screen inaccordance with an embodiment of the present invention. FIG. 157 showsplots for six different pulse durations (PULSETIME1-PULSETIME 6), andsixteen pulse strength levels (1-16) for each plot.

The control circuit of FIG. 156 includes 4 transistors with respectivevariable resistors R1, R2, R3 and R4. The values of the resistorscontrol the signal levels and the ratio between their values controlsgradients of the pulse curves shown in FIG. 156.

Reference is made to FIG. 158, which is a simplified pulse diagram and acorresponding output signal graph, for calibrating a light-based touchscreen, in accordance with an embodiment of the present invention. Thesimplified pulse diagram is at the left in FIG. 158, and shows differentpulse durations, t₀, . . . , t_(N), that are managed by a controlcircuit when calibrating the touch screen. As shown in FIG. 158,multiple gradations are used to control duration of a pulse, andmultiple gradations are used to control the pulse current. Thecorresponding output signal graph is at the right in FIG. 158.

As shown in FIG. 158, different pulse durations result in different risetimes and different amplitudes. Signal peaks occur close to the timewhen the analog-to-digital (A/D) sampler closes its sample and holdcircuit. In order to obtain a maximum output signal, the emitter pulseduration is controlled so as to end at or near the end of the A/Dsampling window. Since the A/D sampling time is fixed, the timing,t_(d), between the start of A/D sampling and the pulse activation timeis an important factor.

Assembly of Touch Screen Components

As described hereinabove, a minimum of tolerances are required whenaligning optical guides that focus on respective light emitters andlight receivers, in order to achieve accurate precision on a light-basedtouch screen. A small misalignment can severely degrade accuracy oftouch detection by altering the light beam. It is difficult toaccurately place a surface mounted receiver and transmitter such thatthey are properly aligned with respective light guides.

Because of this difficulty, in an embodiment of the present invention, alight guide and transmitter or receiver are combined into a singlemodule or optical element, as described above with reference to FIGS.115-118.

In some instances it may be of advantage not to combine an emitter or areceiver into an optical element, e.g., in order to use standard emitterand receiver components. In such instances precision placement ofcomponents is critical.

In some embodiments of the present invention, the optical lens thatincludes the feather pattern is part of a frame that fits over thescreen. FIG. 46 shows a cross-section of such a frame 455, which isseparate from LED 200.

Reference is made to FIG. 159, which is an illustration showing how acapillary effect is used to increase accuracy of positioning acomponent, such as an emitter or a receiver, on a substrate, inter aliaa printed circuit board or an optical component, in accordance with anembodiment of the present invention. Shown in FIG. 159 is an emitter ora receiver 398 that is to be aligned with an optical component ortemporary guide 513. Optical component or temporary guide 513 is fixedto a printed circuit board 763 by guide pins 764. Solder pads 765 areplaced at an offset from component solder pads 766. Printed circuitboard 763 is then inserted into a heat oven for soldering.

Reference is made to FIG. 160, which is an illustration showing theprinted circuit board 763 of FIG. 159, after having passed through aheat oven, in accordance with an embodiment of the present invention. Asshown in FIG. 160, component 398 has been sucked into place by thecapillary effect of the solder, guided by a notch 768 and a cavity 769in optical component or temporary guide 513. When a temporary guide isused, it may be reused for subsequent soldering.

The process described with reference to FIGS. 159 and 160 is suitablefor use in mass production of electronic devices.

ASIC Controller for Light-Based Touch Screens

Aspects of the present invention relate to design and use of aprogrammable state machine for novel light-based touch screen ASICcontrollers that execute a scanning program on a series of emitters anddetectors. The scanning program determines scan sequence, current levelsand pulse widths. The controller includes integrated LED drivers for LEDcurrent control, integrated receiver drivers for photo detector currentmeasurement, and an integrated A/D convertor to enable communicationbetween the controller and a host processor using a standard businterface, such as a Serial Peripheral Interface (SPI).

In accordance with the present invention, a program is loaded onto thecontroller, e.g., over SPI. Thereafter, scanning execution runsindependently from the host processor, optimizing overall system powerconsumption. When the scan data are ready, the controller issues aninterrupt to the host processor via an INT pin.

Reference is made to FIG. 161, which is a simplified illustration of alight-based touch screen 800 and an ASIC controller therefor, inaccordance with an embodiment of the present invention.

Reference is made to FIG. 162, which is a circuit diagram of a chippackage 731 for a controller of a light-based touch screen, inaccordance with an embodiment of the present invention.

As shown in FIG. 162, chip package 731 includes emitter driver circuitry740 for selectively activating a plurality of photoemitters 200 that areoutside of the chip package, and signal conducting pins 732 forconnecting photoemitters 200 to emitter driver circuitry 740. Emitterdriver circuitry 740 is described in applicants' co-pending patentapplication U.S. Ser. No. 12/371,609 entitled LIGHT-BASED TOUCH SCREENfiled on Feb. 15, 2009, the contents of which are hereby incorporated byreference. Inter alia, reference is made to paragraphs [0073],paragraphs [0087]-[0091] and FIG. 11 of this application as published inU.S. Publication No. 2009/0189878 A1 on Jul. 30, 2009.

Emitter driver circuitry 740 includes circuitry 742 for configuringindividual photoemitter pulse durations and pulse currents for eachemitter-detector pair via a programmable current source. Circuitry 742is described in applicants' co-pending patent application U.S. Ser. No.13/052,511 entitled LIGHT-BASED TOUCH SCREEN WITH SHIFT-ALIGNED EMITTERAND RECEIVER LENSES filed on Mar. 21, 2011, the contents of which arehereby incorporated by reference. Inter alia, reference is made toparagraphs [0343]-[0358] and FIGS. 99-101 of this application aspublished in U.S. Publication No. 2011/0163998 on Jul. 7, 2011.

Chip package 731 includes detector driver circuitry 750 for selectivelyactivating a plurality of photo detectors 300 that are outside of thechip package, and signal conducting pins 733 for connecting photodetectors 300 to detector driver circuitry 750. Detector drivercircuitry 750 includes circuitry 755 for filtering current received fromphoto detectors 300 by performing a continuous feedback bandpass filter,and circuitry 756 for digitizing the bandpass filtered current.Circuitry 755 is described inter alia at paragraphs [0076], paragraphs[107]-[0163] and FIGS. 14-23B of the above-referenced U.S. PublicationNo. 2009/0189878 A1. Chip package 731 also includes detector signalprocessing circuitry 753 for generating detection signals representingmeasured amounts of light detected on photo detectors 300.

Chip package 731 further includes I/O pins 736 for communicating with ahost processor 772. Chip package 731 further includes controllercircuitry 759 for controlling emitter driver circuitry 740 and detectordriver circuitry 750. Controller circuitry 759 communicates with hostprocessor 772 using a bus standard for a Serial Peripheral Interface(SPI) 775. Chip package 731 further includes a chip select (CS) pin 737for coordinating operation of controller circuitry 759 with at least oneadditional controller 774 for the light-based touch screen.

The controller shown in FIG. 162 packages all of the above mentionedelements within chip package 731, (i) thereby enabling automaticexecution of an entire scan sequence, such as 52 emitter-receiver pairs,and (ii) thereby storing the detection signals in a register arraylocated in controller circuitry 759, for subsequent analysis by hostprocessor 772. This register array provides storage for at least 52,12-bit receiver results. Additional registers in controller circuitry759 are provided for configuring individual pulse durations and pulsecurrents for individual emitter-receiver pairs. In order to support 52unique emitter-receiver pairs, at least 104 registers are provided;namely, 52 registers for configuring individual pulse durations, and 52registers for configuring individual pulse currents.

Reference is made to FIG. 163, which is a circuit diagram for six rowsof photo emitters with 4 or 5 photo emitters in each row, for connectionto pins 732 of chip package 731, in accordance with an embodiment of thepresent invention. The 11 lines LED_ROW1, . . . , LED_ROW6 and LED_COL1,. . . , LED_COL5 provide two-dimensional addressing for 26 photoemitters, although the photo emitters are physically arranged around twoedges of the touch screen, as shown in FIG. 150. TABLE IV shows LEDmultiplex mapping from photo emitter LEDs to LED_ROW and LED_COL pins.More generally, an LED matrix may include an m×n array of LEDs supportedby m+n I/O pins on the controller.

As such, an LED is accessed by selection of a row and a column I/O pin.The controller includes push-pull drivers for selecting rows andcolumns. It will be appreciated by those skilled in the art that the rowand column coordinates of the LEDs are unrelated to the physicalplacement of the LEDs and the push-pull drivers. In particular, the LEDsdo no need to be physically positioned in a rectangular matrix.

In an alternative embodiment of the controller of the present invention,current source drivers are used instead of push-pull drivers. In anotherembodiment of the controller of the present invention, some of thepush-pull drivers are combined with current source drivers, and othersof the push-pull drivers are combined with current sink drivers.

TABLE IV LED multiplex mapping to LED_ROW and LED_COL pins LED LED_ROWpin enabled LED_COL pin enabled 1 1 1 2 2 1 3 3 1 4 4 1 5 5 1 6 6 1 7 12 8 2 2 9 3 2 10 4 2 11 5 2 12 6 2 13 1 3 14 2 3 15 3 3 16 4 3 17 5 3 186 3 19 1 4 20 2 4 21 3 4 22 4 4 23 5 4 24 6 4 25 1 5 26 2 5

Advantages of having a dedicated controller for emitters and receiversin a light-based touch screen are power savings and performance. Inconventional systems, a conventional chip, such as the MSP430 chipmanufactured by Texas Instruments of Dallas, Tex., controls emitters andreceivers. Regarding power savings, conventional chips do not provideaccess to all of the power consuming chip elements. Moreover, withconventional chips it is not possible to power on and off externalelements in sync with the emitters. For example, with a conventionalchip the amplifier unit connected to the receivers and theanalog-to-digital convertor (ADC) for digitizing receiver lightdetection current, cannot be turned on and off in sync with activationof the emitters. In conventional systems, these elements are leftpowered on throughout an entire scan sequence. In distinction, thededicated controller of the present invention is able to power theseelements on and off at a resolution of microseconds, in sync withemitter activation. This and other such selective activation ofcontroller blocks, reduce the total power consumption of the touchsystem considerably. In fact, power consumption for the amplifier, theADC and other controller blocks is reduced to the extent that theircollective power consumption is negligible as compared to photoemitteractivation power. As such, system power consumption is nearly the sameas the power consumption for activating the photoemitters.

When the dedicated controller of the present invention scans a series ofemitter-receiver pairs, an LED driver supplies an amount of current toan LED in accordance with settings in LED current control registers andLED pulse length control registers. TABLE V shows the power consumptionof the dedicated controller, for 50 emitter-receiver pairs at 100 Hzwith a power source of 2.7V. Pulse durations and pulse currents are setvia circuitry 742 using configuration registers. Current consumption iscalculated as100 Hz×50 activation pairs×pulse duration (ρs)×pulse current (A)=currentconsumption (ρA) from the battery.Power consumption is calculated as current consumption (ρA)*voltage(V)=power (mW).

TABLE V Photometer power consumption for 50 emitter-receiver pairs at100 Hz with 2.7 V power source Pulse Pulse Current duration (μs) current(A) consumption (μA) Power (mW) 0.125 0.05 31.25 0.084375 0.25 0.05 62.50.16875 0.5 0.05 125 0.3375 1 0.05 250 0.675 2 0.05 500 1.35 4 0.05 10002.7 0.125 0.1 62.5 0.1685 0.25 0.1 125 0.3375 0.5 0.1 250 0.675 1 0.1500 1.35 2 0.1 1000 2.7 4 0.1 2000 5.4 0.125 0.2 125 0.3375 0.25 0.2 2500.675 0.5 0.2 500 1.35 1 0.2 1000 2.7 2 0.2 2000 5.4 4 0.2 4000 10.80.125 0.4 250 0.675 0.25 0.4 500 1.35 0.5 0.4 1000 2.7 1 0.4 2000 5.4 20.4 4000 10.8 4 0.4 8000 21.6

Regarding performance, the time required to complete a scan of allemitter-receiver pairs around the screen is critical, especially forfast stylus tracing. Reference is made to FIG. 164, which is asimplified illustration of a touch screen surrounded by emitters 200 andreceivers 300, in accordance with an embodiment of the presentinvention. Emitters 200 are scanned in a scan sequence; e.g., emitters200 may be scanned in the numbered order 1-16 shown in FIG. 164. Touchpoints 900 correspond to touches made by a person writing his signaturein a fast scrawl using a fine-point stylus. Three locations areindicated for touch points 900. At a time t1, when emitter 1 isactivated, the stylus is located at a location a. At a time t2, whenemitter 16 is activated, the stylus is located at a location b, due tothe quick movement as the user signs his name. However, the detectedlocation on the screen at time t2 is a location c, different thanlocation b; because at time t2, when emitter 16 is activated, the stylushas moved from its location at time t1. Such time lag betweenx-coordinate detection and y-coordinate detection produces errors indetecting touch positions of the stylus on the screen. These errors aremost pronounced with fast stylus writing. As such, it is desirable tocomplete an entire scan sequence as fast as possible.

The dedicated controller of the present invention completes a scansequence faster than conventional chips. The dedicated controller of thepresent invention includes register arrays that store necessaryparameters to execute an entire scan sequence automatically. Thededicated controller further includes a register array for storingfiltered, digital results for a scan sequence. In distinction, withconventional chips not all registers are available, and configurationdata in registers is not automatically parsed. Thus, during a scansequence using conventional chips, some cycles are required forconfiguring further emitter activations and for reading results.

In accordance with an embodiment of the present invention, forconfigurations where the number of emitters and receivers is larger thanwhat may be supported by a single dedicated controller, multiplecontrollers are used. The multiple controllers are each configured priorto executing a scan, and then a scan is executed by each controller inrapid succession. For this embodiment, after configuring registers inall controllers, a host selects a first controller chip, using thechip-select (CS) pin shown in FIG. 162, and activates that chip. Whenthe scan sequence on that chip is completed, the chip sends an interruptto the host. The host then selects a second controller chip using its CSpin, and runs the second chip's scan sequence. After all of thecontroller chips have completed their respective scans, the host readsthe results from each chip and calculates touch locations.

In this regard, reference is made to FIG. 165, which is a simplifiedapplication diagram illustrating a touch screen configured with twocontrollers, indicated as Device 1 and Device 2, in accordance with anembodiment of the present invention. Shown in FIG. 165 is touch screen800 surrounded with LEDs and shift-aligned PDs. Twenty-six LEDs,LED₁-LED₂₆, are connected along a first screen edge to LED pins fromDevice 1, and additional LEDS, LED₁-LED_(CR), along this edge areconnected to LED pins from Device 2. Along the opposite edge, PDs areshift-aligned with the LEDs. PDs that detect light from the Device 1LEDS are connected to Device 1 PD pins, and PDs that detect light fromDevice 2 LEDs are connected to Device 2 PD pins. The dashed linesconnecting each LED to two PDs show how light from each LED is detectedby two PDs. Each PD detects light from two LEDs.

As shown in FIG. 165, PD₂₇ of Device 1 detects light from LED₂₆ ofDevice 1 and also from LED₁ of Device 2. As such, PD₂₇ is connected tothe PD₂₇ pin of Device 1 and also to the PD₁ pin of Device 2. Whendetecting light from LED₂₆ of Device 1, PD₂₇ is sampled over the PD₂₇pin of Device 1 and its result is stored on Device 1; and when detectinglight from LED₁ of Device 2, PD₂₇ is sampled over the PD₁ pin of Device2 and its result is stored on Device 2. As such, each controllercoordinates LED activation with respective PD activation. The hostprocessor calculates touch locations along the Device 1-Device 2 borderby interpolating the PD results from the two devices.

Reference is made to FIG. 166, which is a graph showing performance of ascan sequence using a conventional chip vs. performance of a scan usinga dedicated controller of the present invention. The duration of eachcomplete screen scan is longer with the conventional chip than with thededicated controller. The dedicated controller can be powered downbetween scan sequences, providing further power savings, especiallysince the stretches of time between scan sequences may be larger withuse of the dedicated controller than with use of a conventional chip. Toconnect touch points of multiple scans, the host processor may usespline interpolation or such other predictive coding algorithms, togenerate smooth lines that match the user's pen strokes. Of significanceis that each touch point is very accurate, when using a dedicatedcontroller of the present invention.

Moreover, it is apparent from FIG. 166 that a host using a dedicatedcontroller of the present invention may increase the scan frequencybeyond the limits possible when using a conventional chip. E.g., a hostcan scan 50 emitter receiver pairs at 1000 Hz, using a controller of thepresent invention. In distinction, touch screens using convention chipstypically operate at frequencies of 100 Hz or less. The high samplingrate corresponding to 1000 Hz enables accurate touch locationcalculation over time. In turn, this enables temporal filtering of touchcoordinates that substantially eliminates the jitter effect describedabove when a stylus remains stationary, while substantially reducing thelag time described above between a stylus location and a linerepresenting the stylus' path along the screen.

Such high sampling rates on the order of 50 emitter-receiver pairs at1000 Hz cannot be achieved if individual LEDs require configurationprior to activation. The dedicated controller of the present inventionachieves such high sampling rates by providing the registers and thecircuitry to automatically activate an entire scan sequence.

A further advantage of completing multiple scan sequences in a shorttime is disambiguation of touch signals. The problem of ambiguoussignals is described above with reference to FIGS. 15 and 16. Asexplained above, the same detection pattern of photo detectors isreceived for two concurrent touches along a screen diagonal, asillustrated in FIGS. 15 and 16. When placing two fingers on the screen,there is an inherent delay between the first and second touches.Completing multiple scan sequences in a very short time allows thesystem to determine the first touch, which is unambiguous. Then,assuming that the first touch is maintained when the second touch isdetected, the second touch location is easily resolved. E.g., if it isdetermined that one touch is in the upper left corner and the touchdetection pattern is as shown in FIGS. 15 and 16, then the second touchlocation must be at the lower right corner of the screen.

Thus it will be appreciated by those skilled in the art that a dedicatedcontroller in accordance with the present invention is power-efficient,highly accurate and enables highs sampling rates. The host configuresthe controller for low power, corresponding to 100 Hz or less, or forhigh frequency scanning, such as 500 Hz-1000 Hz.

Determination of which configuration is appropriate is based inter aliaon the area of the touch screen covered by a touch pointer, since jitterand lag are less prominent for a touch covering a relative large area,such as a finger touch, than for a touch covering a relatively smallarea, such as a stylus touch. Based on the area covered by the pointer,as determined by the size of the shadowed area of light-based touchscreen signals, the host determines whether a finger or a stylus isbeing used, and configures an appropriate scan rate based on thetrade-off between power and accuracy.

In accordance with an embodiment of the present invention, the dedicatedcontroller includes scan range registers for selectively activatingLEDs, and current control and pulse duration registers for specifying anamount of current and a duration, for each activation. The scan rangeregisters designate a first LED and a first PD to be activated alongeach screen edge, the number of LEDs to be activated along each edge,and the step factor between activated LEDs. A step factor of 0 indicatesthat at each step the next LED is activated, and a step factor of 1indicates that every other LED is activated. Thus, to activate only oddor only even LEDs, a step factor of 1 is used. Step factors of 2 or moremay be used for steps of 2 or more LEDs, respectively. An additionalregister configures the number of PDs that are activated with each LED.A value of 0 indicates that each LED is activated with a singlecorresponding PD, and a value of 1 indicates that each LED is activatedwith two PDs. The number of PDs activated with each LED may be as manyPD that are available around the touch screen.

To save power, it is advantageous to have a low resolution scan mode fordetecting an initial touch location. The host may run in this mode, forexample, when no touch is detected. When a touch is detected, the hostswitches to a high resolution scan mode, in order to calculate a precisetouch location, as described above with reference to FIG. 136. In termsof controller scan sequence registers, every emitter is activated, i.e.,step=0, with one receiver. The scan sequence of FIG. 136(d) differs fromthat of FIG. 136(e) in the initial PD used in the sequence on eachscreen edge. Specifically, the first PD, namely, PD0, is used in FIG.136(d), and the second PD, namely, PD1, is used in FIG. 136(e). Theinitial PD to be used along each screen edge is configured by aregister.

When each LED is activated with more than one PD, the LED is activatedseparately for each of the PDs. Each such separate activation hasrespective current control and pulse duration registers.

The controller of the present invention automatically controls a mux todirect current to desired LEDs. The LED mux control is set by the scancontrol registers. The controller automatically synchronizes the correctPD receivers when the drivers pulse the LEDS. Twelve-bit ADC receiverinformation is stored in PD data registers. Upon completion of scanning,the controller issues an interrupt to the host processor, andautomatically enters standby mode. The host then reads receiver data forthe entire scan sequence over the SPI interface.

In some touch screen configurations, emitters are shift-aligned withreceivers, with emitters being detected by more than one receiver andbeing activated one or more times for each detecting receiver. Forexample, an emitter may be activated three times in rapid succession,and with each activation a different receiver is activated. Moreover, areceiver is further activated during the interval between emitteractivations to determine an ambient light intensity.

In other touch screen configurations, emitters and receivers arealigned, but each emitter is detected by more than one receiver, andeach emitter is activated separately for each detecting receiver.Emitter-receiver activation patterns are described in applicants'co-pending patent application U.S. Ser. No. 12/667,692 entitled SCANNINGOF A TOUCH SCREEN filed on Jan. 5, 2010, the contents of which arehereby incorporated by reference. Inter alia, reference is made toparagraphs [0029], [0030], [0033] and [0034] of this application aspublished in U.S. Publication No. 2011/0043485 on Feb. 24, 2011.

Reference is made to FIG. 167, which is a simplified illustration of atouch screen 800 having a shift-aligned arrangement of emitters andreceivers, in accordance with an embodiment of the present invention.Shown in FIG. 167 are emitters 204-208 along the south edge of screen800, shift-aligned receivers 306-311 along the north edge of screen 800,emitters 209-211 along the east edge of screen 800, and shift-alignedreceivers 312-315 along the west edge of screen 800. It is noted thateach edge of receivers has one or more receivers than the number ofemitters along the opposite edge, in order to detect touches in thecorners of screen 800. A beam 174 depicts activation of emitter 204 anddetection by receiver 306. TABLE VI lists an activation sequence interms of emitter-receiver pairs.

TABLE VI Activation sequence of emitter-receiver pairs Activation No.Emitter Receiver 1 204 306 2 204 307 3 205 307 4 205 308 5 206 308 6 206309 7 207 309 8 207 310 9 208 310 10 208 311 11 209 312 12 209 313 13210 313 14 210 314 15 211 314 16 211 315

Activation no. 10, 208-311, is the last activation along the horizontaldimension of screen 800. Activation no. 11 is the first activation alongthe vertical dimension of screen 800. Such turning of a corner altersthe activation pattern along screen edges. Specifically, the activationpattern along a screen edge is of the form AA-AB-BB-BC-CC-CD . . . ,where the first letter of each pair designates an emitter and the secondletter designates a receiver. Thus in AA-AB a same emitter is activatedwith two receivers, and in AB-BB two emitters are activated with a samereceiver. When turning a corner, as at activation no. 11, the pattern isreset. The active emitter, 209, is not detected by the previouslyactivated receiver 311, since emitter 209 and receiver 311 are notsituated along opposite screen edges. Instead, emitter 209 is detectedby receiver 312, thus starting a new AA-AB-BB-BC . . . activationpattern along the vertical screen dimension. The controller handles apattern reset based on the scan sequence registers, which indicate whena scan along a screen edge is complete.

Reference is made to FIG. 168, which is a simplified diagram of a touchscreen 800 having alternating emitters and receivers along each screenedge, in accordance with an embodiment of the present invention. Asshown in FIG. 165, each emitter is situated between two receivers,resulting in n emitters and n+1 receivers along a given edge, for somenumber n. FIG. 165 shows touch screen 800 surrounded by ten emitters204-213 and fourteen receivers 306-319. As described above withreference to FIG. 164, each emitter is paired with two receivers. Thedotted arrows 174 and 175 in FIG. 168 indicate two activations ofemitter 204; namely, an activation detected by receiver 316, and anotheractivation detected by receiver 315.

In accordance with an embodiment of the present invention, when anactivation sequence arrives at the end of a sequence of emitters along ascreen edge, the activation pattern is restarted when activatingemitters along an adjacent edge. In accordance with another embodimentof the present invention, the angle of orientation of each emitter witha detecting receiver is substantially 45° from the normal to the edgealong which the emitter is arranged. In such case, a receiver along anadjacent edge is operative to detect light from an emitter near a screencorner. As such, the activation pattern is not restarted, but insteadcontinues as a series of activated emitters turn a corner.Alternatively, the controller may restart the activation pattern whenturning a corner by use of registers to store the index of the last LEDto be activated by the controller along each screen dimension.

In accordance with an embodiment of the present invention, thecontroller is a simple state machine and does not include a processorcore, such as an ARM core. As such, costs of controllers of the presentinvention are low. A light-based touch screen using a controller of thepresent invention costs less than a comparable capacitive touch screen,since a capacitive touch screen requires a processor core in order tointegrate a large number of signals and calculate a touch location. Inorder to achieve a quick response time, a capacitive touch screen uses adedicated processor core to calculate a touch location, instead ofoffloading this calculation to a host processor. In turn, this increasesthe bill of materials for capacitive touch screens. In distinction,light-based touch screens of the present invention use two neighboringreceiver values to calculate a touch location along an axis, whichenables the host to calculate a touch location and, consequently,enables use of a low-cost controller.

In accordance with an embodiment of the present invention, multiplecontrollers may be operative to control touch screen 800. As mentionedabove, chip package 731 includes a chip select (CS) pin 737 forcoordinating operation of scanning controller circuitry 759 with atleast one additional controller 774 for the light-based touch screen.

In accordance with embodiments of the present invention, the controllersupports activation sequences for the touch screen of configuration no.6 described hereinabove. In a first embodiment, emitters are positionedalong two screen edges, directly opposite respective receivers along theremaining two screen edges, as shown in FIG. 63. Each emitter sends atwo-pitch wide light beam to its respective receiver. An opticalelement, such as element 530 described hereinabove with reference toFIG. 64, interleaves this wide beam with neighboring wide beams, togenerate two sets of overlapping wide beams that cover the screen; e.g.,the set including every second beam covers the screen. FIG. 69 shows acontiguous area covered by beams 168 and 169 generated by respectiveemitters 201 and 202, with emitter 200 between them.

Two activation sequences are provided; namely, an activation sequencefor low-resolution detection when no touch is detected, and anactivation sequence for high resolution detection for tracing one ormore detected touches. In low-resolution detection every secondemitter-receiver pair is activated along one screen edge. For arectangular screen, the shorter edge is used. In order to distribute useof components uniformly, odd and even sets of emitter-receiver pairs areactivated alternately. Thus in low-resolution detection each emitter isconfigured to be activated with one receiver, and the step factor is 1;i.e., every second emitter is activated. In high resolution detectionmode each emitter is configured to be activated with one receiver, andthe step factor is 0; i.e., every emitter is activated. The scan in thismode activates emitters along both emitter-lined screen edges.

In an alternative embodiment, emitters and receivers are alternatedalong screen edges, as shown in FIG. 79. Each emitter sends a two-pitchwide beam to its respective receiver. An optical element, such aselement 530 described hereinabove with reference to FIG. 64, interleavesthis wide beam with neighboring wide beams, to generate two sets ofoverlapping wide light beams that cover the screen; e.g., the setincluding every second beam covers the screen. FIG. 78 shows acontiguous area covered by beams 168 and 169 generated by respectiveemitters 201 and 202, with receiver 300 between them.

In this embodiment three activation sequences are provided; namely, anactivation sequence for low-resolution detection using detection on oneaxis, an activation sequence for high resolution detection usingdetection on two axes, and an activation sequence for high resolutiondetection using detection in four axes. In low-resolution detectionevery second emitter-receiver pair is activated along one screen edge.For a rectangular screen, the shorter edge is used. In order todistribute use of components uniformly, odd and even sets of beams areactivated alternately. However, because neighboring beams are aimed inopposite directions, the emitters are connected to the ASIC LEDconnectors in such a way that the index of emitters is configured toincrement along a single screen edge. Thus the step factor is 0; i.e.,every second beam is activated, and the activation series ends at thelast emitter along the active edge. In an alternative embodiment theemitters are connected to the ASIC LED connectors such that the index ofemitters is configured to increment together with the series of beams.In this case the step factor is 1; i.e., every second beam is activated.

In high resolution detection mode using beams along two axes, eachemitter is configured to be activated with one respective receiver, thestep factor is 0, and the activation series covers all emitters.

In high resolution detection mode using beams along four axes, multipleactivations are executed. A first activation activates beams along thehorizontal and vertical axes. The initial emitter index matches theinitial receiver index, and the emitter index increments together withthe receiver index. A second activation series activates a first set ofdiagonal beams. In this case, the initial emitter and receiver indicesdefine endpoints of one of the diagonal beams from the initial emitter.The emitter index then increments together with the receiver indexaround the screen. A third activation series activates a second set ofdiagonal beams. In this case, the initial emitter and receiver indicesdefine endpoints of the second diagonal beam from the initial emitter.

Resilient Touch Surfaces

Reference is made to FIG. 169, which is a simplified illustration of atouch surface with a flexible compressible layer on top of the surface,in accordance with an embodiment of the present invention. Light beamsthat cross above the surface to provide touch detection are directedthrough the compressible layer. FIG. 169 shows emitters 200 andreceivers 300 on a PCB 700, and a resilient flexible layer 650 situatedabove a display 642 and bonded to an outer edge of a light guide. Thelight guide has two units, namely, an upper section 463 and a lowersection 464. Generally layer 650 is transparent, to enable viewing ofdisplay 462.

Reference is made to FIG. 170, which is a magnified view of the touchsurface of FIG. 169, in accordance with an embodiment of the presentinvention. As shown in FIG. 170, light beam 100 travels from emitter 200through light guide units 463 and 464, and into flexible layer 650.Light beam 100 is detected at the opposite edge of the surface by arespective receiver 300, shown in FIG. 169.

Reference is made to FIG. 171, which is a simplified illustration of anobject pressing down on layer 650 of the touch surface of FIG. 169, andcreating an impression thereon, in accordance with an embodiment of thepresent invention. As shown in FIG. 171, a user presses his finger 900on layer 650 and disrupts or frustrates any beam 100 crossing thelocation of the impression before the beam can reach receiver 300. Suchdisruption or frustration of beam 100 has two measurable effects;namely, (i) a diminished detection signal at a corresponding receiver orreceivers 300 at which the beam was directed, and (ii) increaseddetection signals at others of the receivers that receive the frustratedbeams. Moreover, the greater the impression, the greater is thedisruption. As such, the amount of missing expected light at somereceivers and the pattern of increased detection at other receiversindicates the amount of pressure exerted by finger 900 on layer 650.

When layer 650 is formed as a single gel-like body, a deep impression,created by a large amount of downward pressure, has a wider radius thana shallow impression. In turn, the amount of light detected at thereceivers indicates the width of the radius, which determines the amountof downward force applied by finger 900. In general, the pattern ofblocked and frustrated beams created by an impression into atransmissive body, as in embodiments of the present invention, is moresubstantial than the frustrated total internal reflection of lighttransmitted into a rigid body when an object teaches the surface of thetransmissive body but does not form an impression therein.

Reference is made to FIG. 172, which is a simplified illustration of analternative touch surface with a flexible compressible layer on top ofthe surface, in accordance with an embodiment of the present invention.In the touch surface of FIG. 172, a flexible layer 650 is flush with anupper edge of light guide unit 463, and is suspended above the surfaceof a display 642, to form an air gap 843. FIG. 172 shows two light beamsemitted from an emitter 200. A first light beam 100 travels throughlayer 650, and a second light beam 101 travels across air gap 843.

Reference is made to FIG. 173, which is a simplified illustration of anobject pressing down on layer 650 of the touch surface of FIG. 172, andcreating an impression thereon, in accordance with an embodiment of thepresent invention. A user pressing his finger 900 into layer 650 fromabove bends the layer and disturbs beam 100. In addition, the bent layerextends into air gap 843 and blocks beam 101.

In an alternative embodiment of the present invention, layer 650 is athin elastic membrane, and only beams inside of air gap 843 are used fortouch detection. In this alternative embodiment, light is not sentthrough the membrane, and the membrane may wrap the device.

In some embodiments of the present invention, a thin transparent elasticmembrane is placed inside a frame that snaps on to and snaps off of atouch surface. In one embodiment, a handset for a police or firedepartment includes a light-based touch surface as described above,which is generally used without an elastic upper layer. However, when apoliceman or fireman encounters a harsh environment, where water ordebris may hit the surface and interfere with touch detections on thesurface, the policeman or fireman snaps on the transparent elasticlayer. The elastic layer protects the surface and prevents water anddebris from reaching the light beams and causing false touch detections.Touches performed through the elastic layer are detected at a coarserresolution than touches performed without the elastic layer, because ofthe tapering of the elastic layer when it is pressed onto the surface bya pointer object. Moreover, often in harsh environments the policeman orfireman is wearing gloves, which also reduces the resolution of thetouch since the surface area of a gloved finger is larger than that of abare finger. For these reasons, in accordance with an embodiment of thepresent invention, a handset of this type provides a high-resolutionuser interface for use without the elastic membrane, and alow-resolution user interface for use with the elastic membrane. Onedifference between a high-resolution and a low-resolution user interfaceis the size and density of buttons presented on the display; namely, alow resolution user interface uses larger buttons that are spacedfarther apart, and a high resolution user interface uses smaller buttonsthat are spaced closer together. A low resolution user interfaceprovides an opportunity to reduce the scan rate, and to reduce thenumber of emitters and receivers used when scanning a surface, vis-à-visa high resolution user interface, since lower touch precision isrequired. In some embodiments of the present invention, the snap-onframe includes an RFID chip, or such other identifier, whereby thehandset detects when the elastic layer is snapped on or off andautomatically toggles the low-resolution/high-resolution user interfaceaccordingly.

Reference is made to FIG. 174, which is a simplified illustration ofanother alternative touch surface with a flexible compressible layer ontop of the surface, in accordance with an embodiment of the presentinvention. FIG. 174 shows the edges of a light guide unit 463 extendingabove a flexible layer 650. A first light beam 100 travels above layer650 and is interrupted when an object touches layer 650. A second lightbeam 101 travels through layer 650, and is interrupted or frustratedonly when an object exerts downward pressure on layer 650, forming animpression thereon. As such, the touch surface of FIG. 174 provides atleast two levels of touch detection; namely, detection of an initialtouch, and detection of a touch with pressure.

It will thus be appreciated by those skilled in the art that embodimentsof the present invention provide several advantages for handset anddisplay manufacturers. A first advantage is having light-based touchsurfaces without raised bezels around the screen, as shown in FIGS.169-172. This advantage is also achieved using an elastic sheetsuspended above the display, as described above. A second advantage ishaving light-based touch surfaces that operate in environments of waterdroplets, dust and dirt. The water, dust and dirt settle on top of layer650, but do not generate a touch signal, since water, dust and dirt donot create impressions in layer 650. A third advantage is havinglight-based touch surfaces that provide tactile sensations to a userpressing a finger or stylus into the surface, by using an upper layer ofsemi-hard gel that cradles an object pressed upon it. The semi-hardlayer transmits haptic feedback from the device to the user's finger orstylus. A semi-hard material transmits more compelling haptic sensationsto the user than do the rigid plastic and glass surfaces used in priorart touch surface devices.

Touch surfaces in accordance with the present invention may bemanufactured by performing a double injection mold of the light guide,referred to as “overmolding”, with a soft material such as inter aliasilicon, optically clear adhesive, or a bladder filled with a liquid.Overmolding mates the light guide and the soft material in a singleprocess or tool, and reduces cost as compared with manufacturing a lightguide and a flexible layer in two separate processes.

Light guides in accordance with the present invention may be made interalia of polycarbonate or a cyclic olefin copolymer (COC) having a highglass transition temperature. COC has better optical properties thanpolycarbonate, better chemical resistance, better flow in the moldproperties, and lower shrinkage values, reducing the risk of sink marks.Thus COC provides flexibility in light guide design as well as highyield.

The present invention has broad application to electronic devices withtouch sensitive screens, including small-size, mid-size and large-sizescreens. Such devices include inter alia computers, home entertainmentsystems, car entertainment systems, security systems, PDAs, cell phones,electronic games and toys, digital photo frames, digital musicalinstruments, e-book readers, TVs and GPS navigators.

In the foregoing specification, the invention has been described withreference to specific exemplary embodiments thereof. It will, however,be evident that various modifications and changes may be made to thespecific exemplary embodiments without departing from the broader spiritand scope of the invention as set forth in the appended claims.Accordingly, the specification and drawings are to be regarded in anillustrative rather than a restrictive sense.

What is claimed is:
 1. A touch input device, comprising: a housing; anelastic layer at which depression by an object causes a localindentation in the elastic layer, the geometry of the local indentationbeing in accordance with the object's force of depression; one or morelight emitters mounted in said housing; one or more light detectorsmounted in said housing; a light guide positioned between said emittersand said elastic layer, that directs light beams from said emitters intosaid elastic layer at an angle such that the light beams, after enteringsaid elastic layer, remain confined to said elastic layer by totalinternal reflection; a light guide positioned between said detectors andsaid elastic layer, that directs light beams exiting said elastic layeronto said detectors, each detector having a reference output valuecorresponding to an expected amount of light detection when saidemitters are activated and no object is touching said elastic layer; anda processor, mounted in said housing and connected to said lightdetectors, determining the object's force of depression based on thegeometry of the local indentation in the elastic layer, as calibrated bya deviation between actual and reference output values for one of saiddetectors; wherein said processor further determines a depth of thelocal indentation.
 2. The touch input device of claim 1, wherein thedeviation comprises an actual output value from a light detector that isless than the reference output value for that detector.
 3. The touchinput device of claim 1, wherein the deviation comprises an actualoutput value from a light detector that is greater than the referenceoutput value for that detector.
 4. The touch input device of claim 1,wherein said processor further determines a location of the localindentation.
 5. The touch input device of claim 1, wherein said elasticlayer is transparent, further comprising a display mounted in saidhousing underneath said elastic layer.
 6. The touch input device ofclaim 1, wherein the deviation comprises an actual output value from afirst of said light detectors that is less than the reference outputvalue for that first detector, and an actual output value from a secondof said light detectors that is greater than the reference output valuefor that second detector.
 7. The touch input device of claim 1, whereinsaid elastic layer comprises a semi-hard gel.
 8. The touch input deviceof claim 1, wherein said light guides are comprised of a differentmaterial than said elastic layer, and wherein said light guides and saidelastic layer are manufactured by a single over-molding process.
 9. Amethod for providing touch input to an electronic device, comprising:providing an elastic layer at which depression by an object causes alocal indentation in the elastic layer, the geometry of the localindentation being in accordance with the object's force of depression;directing light beams into the elastic layer at one or more locationsalong edges of the elastic layer at an angle such that the light beams,after entering the elastic layer, remain confined to the elastic layerby total internal reflection, and exit the layer at exit locations alongedges of the elastic layer; detecting light beams that exit the elasticlayer at one or more exit locations, each exit location having areference output value corresponding to an expected amount of lightdetection when no object is touching the elastic layer; and determiningthe object's force of depression based on the geometry of the localindentation in the elastic layer, as calibrated by a deviation betweenan actual detected amount of light and a corresponding reference amountof light at one of the exit locations; and determining a depth of thelocal indentation in the elastic layer.
 10. The method of claim 9,wherein the deviation comprises the actual detected amount of light thatis less than the reference amount of light for one of the exitlocations.
 11. The method of claim 9, wherein the deviation comprisesthe actual detected amount of light that is greater than the referenceamount of light for one of the exit locations.
 12. The method of claim9, further comprising determining a location of the local indentation inthe elastic layer.
 13. The method of claim 9, wherein the elastic layeris transparent, further comprising providing a display presenting userinteraction information underneath the elastic layer.
 14. The method ofclaim 9, wherein the deviation comprises the actual detected amount oflight that is less than the reference amount of light at a first exitlocation, and the actual detected amount of light that is greater thanthe reference amount of light at a second exit location.
 15. The methodof claim 9, wherein the elastic layer comprises a semi-hard gel.
 16. Thetouch input device of claim 1, further comprising a haptic driver,mounted in said housing and connected to said elastic layer and to saidprocessor, generating haptic vibrations in said elastic layer at thelocation of the local indentation.
 17. The method of claim 9, furthercomprising generating haptic vibrations in the elastic layer at thelocation of the local indentation, in response to said determining.